- Metabolic coupling of dehydration and decarboxylation in the curacin A pathway: Functional identification of a mechanistically diverse enzyme pair
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This study describes the functional identification of a pair of mechanistically diverse enzymes that catalyze the successive dehydration (CurE ECH1) and decarboxylation (CurF ECH2) of (S)-HMG-ACP to generate a 3-methylcrotonyl-ACP intermediate, the presumed precursor of the cyclopropyl ring in curacin A. The reactions catalyzed by ECH1 and ECH2 are found in a broad cross-section of microbial natural product gene clusters and participate in the introduction of carbon chain branch points and functional group diversity as key steps in the HMG-CoA synthase mediated addition of C-2 from acetate to the β-carbonyl group of polyketide chains. Copyright
- Gu, Liangcai,Jia, Junyong,Liu, Haichuan,Hakansson, Kristina,Gerwick, William H.,Sherman, David H.
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- EFFICIENT PREPARATION OF ALLYLIC GRIGNARD REAGENTS USING SLURRIES OF PRECONDENSED MAGNESIUM
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Using a simple apparatus addition of 2-alkenyl halides to precondensed active Mg in THF gave clean solutions of 2-alkenylmagnesium halides which on carbonation furnished β,γ-unsaturated carboxylic acid in high yields.
- Oppolzer, Wolfgang,Kuendig, Ernest Peter,Bishop, Paul M.,Perret, Celia
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- Reaction of Diketene with Grignard Reagents in the Presence of Cobalt Catalyst. A Convenient Method for the Synthesis of 3-Methylenealkanoic Acids Leading to Terpenoids
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Primary alkyl Grignard reagents react regioselectively with diketene in the presence of cobalt(II) iodide to afford 3-methylenealkanoic acids in good yields.The synthetic utility of this reaction is demonstrated in the syntheses of terpenoids by two methods.Utilizing the isomerization of double bond of 3-methylenealkanoic acids, geranic acid and farnesic acid were obtained in two steps.Another method, the tandem sigmatropic rearrangement of the corresponding allylic esters was used for the synthesis of C18-Cecropia juvenile hormone.
- Fujisawa, Tamotsu,Sato, Toshio,Gotoh, Yoshihiko,Kawashima, Masatoshi,Kawara, Tatsuo
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- Palladium-Catalyzed, Atmospheric Pressure Carbonylation of Allylic Chlorides in Two-Phase Aqueous Sodium Hydroxide-Organic Solvent Media
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The palladium-catalyzed, atmospheric pressure carbonylation of allylic chlorides is realized in aqueous NaOH/benzene.Phosphine complexes PdCl2L2 (I) (a, L=Ph2P(m-C6H4SO3Na; b, L=Ph3P), or Na2PdCl4 can be used as the catalyst.
- Kiji, Jitsuo,Okano, Tamon,Nishiumi, Wataru,Konishi, Hisatoshi
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- Ether cleavage by activated metals II.* Cleavage of allyl and benzyl ethers by activated magnesium
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Activated magnesium (prepared by reduction of magnesium halides with potassium) reacts with allyl and benzyl ethers to give the corresponding allyl or benzyl magnesium compounds.
- Bartmann, Ekkehard
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- Silver encapsulated copper salen complex: Efficient catalyst for electrocarboxylation of cinnamyl chloride with CO2
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An active catalyst, [Cu]?Ag composite, was synthesized for the first time and used as a cathode for electrocarboxylation of cinnamyl chloride with CO2. β,γ-Unsaturated carboxylic acids were obtained with excellent yield and moderate selectivity. Moreover, reasonable yields and selectivities of carboxylic acids were also achieved with several allylic halides and aryl halides.
- Wu, La-Xia,Zhao, Ying-Guo,Guan, Ye-Bin,Wang, Hui,Lan, Yang-Chun,Wang, Huan,Lu, Jia-Xing
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The allyl ethers of α- and β-naphthol are readily cleaved by metallic magnesium in absolute tetrahydrofuran forming allylmagnesium naphtholates in excellent yields. The cleavage of 2-methylallyl β-naphthyl ether, on the other hand, proceeds slowly giving
- Maercker, Adalbert,Jaroschek, Hans-Joachim
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- Organophotoredox/Copper Hybrid Catalysis for Regioselective Allylic Aminodecarboxylation of β,γ-Unsaturated Carboxylic Acids
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A new cooperative organophotoredox/copper catalysis allowing for the conversion of β,γ-unsaturated carboxylic acids into allylic hydrazides via radical regioselective allylic decarboxylative amination is reported. The coexistence of the copper catalyst is essential for the high yield and regioselectivity.
- Manick, Anne-Doriane,Tanaka, Hirotaka,Oisaki, Kounosuke,Kanai, Motomu
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- Synthesis of the sex pheromone of the citrus mealybug, Pseudococcus cryptus
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The sex pheromone of the citrus mealybug (Pseudococcus cryptus), [(1R,3R)-3-isopropenyl-2,2-dimethylcyclobutyl]methyl 3-methyl-3-butenoate, was synthesized from (+)-α-pinene in five operational steps in a 43% overall yield. The synthetic pheromone was identical with the natural pheromone in 1H-NMR and mass spectroscopic properties, and showed almost the same pheromonal activity as the natural pheromone.
- Nakahata, Takashi,Itagaki, Noriaki,Arai, Tomonori,Sugie, Hajime,Kuwahara, Shigefumi
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- Catalytic, contra-Thermodynamic Positional Alkene Isomerization
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The positional isomerization of C═C double bonds is a powerful strategy for the interconversion of alkene regioisomers. However, existing methods provide access to thermodynamically more stable isomers from less stable starting materials. Here, we report
- Occhialini, Gino,Palani, Vignesh,Wendlandt, Alison E.
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supporting information
p. 145 - 152
(2022/01/19)
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- Nickel-catalyzed electrocarboxylation of allylic halides with CO2
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Nickel-catalyzed regioselective electrocarboxylation of allylic halides with CO2at atmospheric pressure has been developed by adjusting reaction parameters, including catalyst, solvent, temperature and additive. β,γ-Unsaturated carboxylic acids were obtained in moderate to good yields and with high chain selectivity. This reaction shows tolerance to functional groups. In addition, cyclic voltammetry was performed to provide the possible mechanism of nickel-catalyzed CO2allylation.
- Wu, La-Xia,Deng, Fang-Jie,Wu, Lin,Wang, Huan,Chen, Tai-Jie,Guan, Ye-Bin,Lu, Jia-Xing
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p. 13137 - 13141
(2021/08/03)
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- Control of β-Branching in Kalimantacin Biosynthesis: Application of 13C NMR to Polyketide Programming
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The presence of β-branches in the structure of polyketides that possess potent biological activity underpins the widespread importance of this structural feature. Kalimantacin is a polyketide antibiotic with selective activity against staphylococci, and its biosynthesis involves the unprecedented incorporation of three different and sequential β-branching modifications. We use purified single and multi-domain enzyme components of the kalimantacin biosynthetic machinery to address in vitro how the pattern of β-branching in kalimantacin is controlled. Robust discrimination of enzyme products required the development of a generalisable assay that takes advantage of 13C NMR of a single 13C label incorporated into key biosynthetic mimics combined with favourable dynamic properties of an acyl carrier protein. We report a previously unassigned modular enoyl-CoA hydratase (mECH) domain and the assembly of enzyme constructs and cascades that are able to generate each specific β-branch.
- Walker, Paul D.,Williams, Christopher,Weir, Angus N. M.,Wang, Luoyi,Crosby, John,Race, Paul R.,Simpson, Thomas J.,Willis, Christine L.,Crump, Matthew P.
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supporting information
p. 12446 - 12450
(2019/08/16)
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- Nickel-Catalyzed 1,2-Diarylation of Simple Alkenyl Amides
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A nickel-catalyzed conjunctive cross-coupling of simple alkenyl amides with aryl iodides and aryl boronic esters is reported. The reaction is enabled by an electron-deficient olefin (EDO) ligand, dimethyl fumarate, and delivers the desired 1,2-diarylated products with excellent regiocontrol. Under optimized conditions, a wide range of amides derived from 3-butenoic acid, 4-pentenoic acid, and allyl amine are compatible substrates. This method represents the first example of regiocontrolled 1,2-diarylation directed by a native amide functional group. Computational analysis sheds light on the potential substrate binding mode and the role of the EDO ligand in the reductive elimination step.
- Derosa, Joseph,Kleinmans, Roman,Tran, Van T.,Karunananda, Malkanthi K.,Wisniewski, Steven R.,Eastgate, Martin D.,Engle, Keary M.
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supporting information
p. 17878 - 17883
(2019/01/04)
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- Telescoped Synthesis of γ-Bromo-β-Lactones from Allylic Bromides Employing Carbon Dioxide
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A direct synthesis of the title compounds involving a stepwise Zn-mediated carboxylation of allylic bromides with CO2 delivering β, γ-unsaturated carboxylic acids and a subsequent bromolactonization is reported. The described method demonstrates the use of readily prepared allylzinc bromides by the method of Knochel for fixation of CO2 employing commodity chemicals and zinc dust. This process was then optimized into a two-stage, telescoped process for the direct synthesis of γ-bromo-β-lactones from allyl bromides. The described strategy delivers functionalized β-lactones with dual reactivity as acylating and alkylating agents, which have utility as synthetic intermediates and are attracting growing interest as proteomic tools for activity-based protein profiling.
- Vellalath, Sreekumar,Romo, Daniel
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p. 335 - 339
(2017/04/13)
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- Isothiourea-mediated asymmetric functionalization of 3-alkenoic acids
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Isothiourea HBTM-2.1 promotes the catalytic asymmetric α- functionalization of 3-alkenoic acids through formal [2 + 2] cycloadditions with N-tosyl aldimines and formal [4 + 2] cycloadditions with either 4-aryltrifluoromethyl enones or N-aryl-N-aroyl diazenes, providing useful synthetic building blocks in good yield and with excellent enantiocontrol (up to >99% ee). Stereodefined products are amenable to further synthetic elaboration through manipulation of the olefinic functionality.
- Morrill, Louis C.,Smith, Samuel M.,Slawin, Alexandra M. Z.,Smith, Andrew D.
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p. 1640 - 1655
(2014/03/21)
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- Construction of the 1,2-dialkenylcyclohexane framework via ireland-claisen rearrangement and intramolecular barbier reaction: Application to the synthesis of ()-geijerone and a diastereoisomeric mixture with its 5-epimer
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The elemene-type terpenoids, which possess various biological activities, contain a syn- or anti-1,2-dialkenylcyclohexane framework. An efficient synthetic route to the syn- and anti-1,2-dialkenylcyclohexane core and its application in the synthesis of ()-geijerone and its diastereomer is reported. Construction of the syn- and anti-1,2-dialkenyl moiety was achieved via Ireland-Claisen rearrangement of the (E)-Allylic ester, and the cyclohexanone moiety was derived from the iodoaldehyde via intramolecular Barbier reaction. The synthetic strategy allows rapid access to various epimers and analogues of elemene-type products.
- Liang, Dawei,Gao, Nana,Liu, Wei,Dong, Jinhua
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p. 1238 - 1249
(2014/02/14)
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- Direct carboxylation of allylic halides with carbon dioxide in the presence of indium
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A highly regioselective indium-mediated allylation of carbon dioxide starting from simple allylic halides (X = I, Br, Cl) has been developed. No transition metal catalyst is needed and an inert atmosphere is not necessary. The reaction tolerates a wide range of synthetically attractive functional groups with a very high branched regioselectivity. The Royal Society of Chemistry 2014.
- Miao, Bukeyan,Ma, Shengming
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supporting information
p. 3285 - 3287
(2014/03/21)
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- Regioselective copper-catalyzed carboxylation of allylboronates with carbon dioxide
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In the presence of a Cu(I)/NHC catalyst, the reactions of allylboronic pinacol esters with CO2 (1 atm) are highly regioselective, giving exclusively the more substituted β,γ-unsaturated carboxylic acids in most cases. A diverse array of substituted carboxylic acids can be prepared via this method, including compounds featuring all-carbon quaternary centers.
- Duong, Hung A.,Huleatt, Paul B.,Tan, Qian-Wen,Shuying, Eileen Lau
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supporting information
p. 4034 - 4037
(2013/09/02)
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- Palladium catalyzed carboxylation of allylstannanes and boranes using CO2
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A family of well-defined (η3-allyl)Pd(L)(carboxylate) (L = PR3 or NHC) complexes are by far the most efficient catalysts reported to date for the catalytic carboxylation of allylstannanes into allylcarboxylates using CO2. The substrate scope of this reaction is extended to both substituted allylstannanes and allylboranes.
- Wu, Jianguo,Hazari, Nilay
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supporting information; experimental part
p. 1069 - 1071
(2011/02/25)
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- Electrocatalytic carboxylation of aliphatic halides at silver cathode in acetonitrile
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A simple and efficient electrocarboxylation reaction of aliphatic halides has been developed using silver as cathode, magnesium as anode and CH3CN saturated CO2 as solvent in an undivided cell. The influence of some key factors (such as the nature of electrode materials, supporting electrolytes and temperature) on this reaction was investigated. Under the optimized condition, the corresponding carboxylic acids were obtained in moderate to good yields (22-89%). The electrochemical behaviour was studied at different electrodes (Ag, Cu, Ni and Ti) by cyclic voltammetry, which showed significant electrocatalytic effect of the silver electrode towards the reductive carboxylation of aliphatic halides.
- Niu, Dong-Fang,Xiao, Li-Ping,Zhang, Ai-Jian,Zhang, Gui-Rong,Tan, Qi-Yun,Lu, Jia-Xing
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p. 10517 - 10520
(2008/12/23)
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- Incorporation of deuterium-labelled analogs of isopentenyl diphosphate for the elucidation of the stereochemistry of rubber biosynthesis
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A series of six deuterium-labelled analogs of isopententyl diphosphate (IPP) was prepared to investigate the detailed stereochemical course of addition of C5 units during rubber biosynthesis in Hevea brasiliensis and Parthenium argentatum. These analogs were incorporated into the cis-polyisoprene chain by rubber transferase in rubber particles, and the stereochemistry was determined by 2H-NMR analysis of the polymer or of levulinic acid derivatives obtained from its ozonolytic degradation. Results indicate that rubber chain elongation occurs with loss of the pro-S hydrogen of IPP, addition of the allylic diphosphate to the si face of IPP and inversion of stereochemistry at the carbon bearing the diphosphate. The Royal Society of Chemistry.
- Scholte, Andrew A.,Vederas, John C.
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p. 730 - 742
(2007/10/03)
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- Novel ester compound and use thereof
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It is an object of the present invention to provide a novel ester compound and the use thereof as a sex attractant. The present invention provides a compound represented by formula (I) described below, and a sex attractant comprising, as an active ingredient, the above compound:
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Page/Page column 3-4
(2008/06/13)
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- Synthesis of 2,6-dideoxysugars via ring-closing olefinic metathesis.
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[formula: see text] Grubbs' RuCl2 (=CHPh)(PCy3)2 (catalyst 1) and RuCl2(=CHPh)(PCy3)(IMess) (catalyst 2) complexes have been successfully utilized in the construction of beta,gamma-unsaturated delta-lactones containing various substitution patterns of methyl groups. Asymmetric dihydroxylation followed by reduction leads to 3,4-cis-dihydroxy-2,6-dideoxypyranoses, which have proven to play very important biological roles as key components of natural products.
- Andreana, Peter R,McLellan, Jason S,Chen, Yongchen,Wang, Peng George
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p. 3875 - 3878
(2007/10/03)
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- Palladium-catalyzed cross-coupling of 3-iodobut-3-enoic acid with organometallic reagents. Synthesis of 3-substituted but-3-enoic acids
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3-Substituted but-3-enoic acids were obtained in good yields under mild experimental conditions by palladium-catalyzed cross-coupling of 3-iodobut-3-enoic acid with organozinc or organotin compounds using PdCl2(MeCN)2 as catalyst and DMF as solvent.
- Abarbri,Parrain,Kitamura,Noyori,Duchene
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p. 7475 - 7478
(2007/10/03)
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- Conjugate addition of organolithium reagents to α,β-unsaturated carbocyclic acids
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Conjugate addition of primary, secondary, tertiary alkyi and phenyl lithium reagents to 2-alkenoic acids affords good yields of branched saturated carboxylic acids. Methyl groups at the α- and β-carbon of the 2-alkenoic acid decrease reactivity as acceptors, and foster deprotonation, respectively. The lithium enediolate resulting from the conjugate addition can react with electrophiles. PM3 calculations are in agreement with the substituent effects.
- Aurell, Maria Jose,Domingo, Luis Ramon,Mestres, Ramon,Munos, Elena,Zaragoza, Ramon Jose
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p. 815 - 830
(2007/10/03)
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- Synthesis of γ-hydroxy α,β-unsaturated amides by base induced isomerization of epoxy amides
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Treatment of 3,4-epoxyamides with LDA affords γ-hydroxy-α,β- unsaturated amides, usually with high (E)-selectivity. The 3,4-epoxyamides were prepared by the epoxidation of β,γ-unsaturated amides with meta- chloroperbenzoic acid.
- Brooks, Peter B.,Marson, Charles M.
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p. 9613 - 9622
(2007/10/03)
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- Transformation of presumptive precursors to frontalin and ex-brevicomin by bark beetles and the West Indian sugarcane weevil (Coleoptera)
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(Z)-6-Nonen-2-one (1) has recently been shown to be the biosynthetic precursor for the aggregation pheromone exo-brevicomin (2) in mountain pine beetle (MPB) males, Dendroctonus ponderosae (Hopkins). We tested the hypotheses that (1) 6-methyl-6-hepten-2-one (3) is the biosynthetic precursor for the aggregation pheromone frontalin (4) in the spruce beetle (SB), Dendroctonus rufipennis (Kirby), and (2) that frontalin and exo-brevicomin are produced from 3 and 1, respectively, only by beetles that utilize them as aggregation pheromones. Exposure of scolytids MPB, SB, pine engraver (PE), Ips pini (Say) and Ips tridens (Mannerheim) and West Indian sugar cane weevil (WISW), Metamasius hemipterus sericeus (Olivier) to deuterio- or protio-3 invariably resulted in the production of deuterio- or protio-4. Similarly, exposure of SB, WISW and I. tridens to 1 resulted in the production of 2. We were unable to demonstrate the presence of 3 in SB volatiles, nor were we able to demonstrate the conversion of 6-methyl-5-hepten-2-one to 3 by SB. Production of enantiomerically enriched frontalin and exo-brevicomin by all the beetles exposed to respective precursors reveals widespread occurrence of nonspecific polysubstrate monooxidases in the Coleoptera.
- Perez,Gries,Gries,Oehlschlager
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p. 445 - 450
(2007/10/03)
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- Activation of C-O and C-N Bonds in Allylic Alcohols and Amines by Palladium Complexes Promoted by CO2. Synthetic Applications to Allylation of Nucleophiles, Carbonylation, and Allylamine Disproportionation
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The direct activation of the C-O bonds in allylic alcohols catalyzed by palladium complexes has been accelerated by carrying out the reactions under CO2. On reaction with diethylamine, allyl alcohol can be converted into N,N-diethylallylamine in the presence of palladium complexes at room temperature under normal pressure of carbon dioxide. Allylation of various carbon nucleophiles such as β-keto esters and β-diketones can be achieved by using allylic alcohols directly in the presence of palladium complexes and CO2. Direct carbonylation of allylic alcohols into unsaturated carboxylic acids can be catalyzed by palladium complexes under the pressure of CO and CO2. Disproportionation of diallylamine into triallylamine and allylamine is also catalyzed by palladium complexes in the presence of CO2. On the basis of studies on the behavior of η3-allylpalladium hydrogencarbonate complexes with the nucleophiles, mechanisms are proposed to account for the palladium-catalyzed allylation processes influenced by CO2.
- Sakamoto, Masato,Shimizu, Isao,Yamamoto, Akio
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p. 1065 - 1078
(2007/10/03)
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- Palladium-Catalyzed, Atmospheric Pressure Carbonylation of Allylic Halides under the Influence of Sodium Hydroxide or Alkoxides. A Facile Synthesis of β,γ-Unsaturated Acids
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The palladium-catalyzed, atmospheric-pressure carboxylation of allylic halides occurs readily in an aqueous sodium hydroxide/organic solvents two-phase system, giving β,γ-unsaturated acids.Phosphine complexes (I, L=m-(Ph2P)C6H4SO3Na; II, L=Ph3P) or Na2 (III) can be used as the catalyst.Atmospheric-pressure alkoxycarbonylation is realized under the influence of a homogeneous alcoholic solution of sodium alkoxide.Phosphine-free palladium complexes, such as 2 or III, are the favored catalyst. β,γ-Unsaturated esters are obtained in high yields.
- Okano, Tamon,Okabe, Nobuyuki,Kiji, Jitsuo
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p. 2589 - 2593
(2007/10/02)
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- Oxidative Cleavage of Indane-1,2,3-trione-Ene Adducts; a Convenient Synthesis of Allyl and Allenyl Carboxylic Acids
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The ene adducts formed by the thermal reaction of indane-1,2,3-trione with olefins or terminal alkynes are cleaved in good yield by reaction with periodic acid in dry diethyl ether.Thereby the 2-hydroxyindane-1,2-dione moiety in the adduct is replaced by a CO2H group; hence indane-1,2,3-trione is a masked equivalent of carbon dioxide in the ene reaction.The allyl or allenyl carboxylic acid may be separated from the co-products (phthalic acid and anhydride) by extraction into hexane.
- Gill, G. Bryon,Idris, Muhammad S. Hj.,Kirollos, Kirollos S.
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p. 2367 - 2370
(2007/10/02)
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- KINETIC RESOLUTION OF RACEMIC β,γ-EPOXY ESTERS WITH PIG LIVER ESTERASE (PLE, E.C. 3.1.1.1.)
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The β,γ-epoxy esters (+/-)-2 to (+/-)-6 were synthetisized.The E-values of kinetic resolution of 2, 3, 4, and 6 with PLE and the absolute configuration of the products of the hydrolysis were determined by the conversion to known compounds.
- Mohr, Peter,Roesslein, Lukas,Tamm, Christoph
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p. 2513 - 2516
(2007/10/02)
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- SUR LA REGIO SELECTIVITE DE LA REACTION DU BENZALDEHYDE AVEC LES ORGANOZINQUES ISSUS DU γ-BROMOCROTONATE ET DU γ-BROMOSENECIOATE DE TRIMETHYLSILYLE
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The regioselectivity of the reaction of organozinc compounds derived from γ-bromocrotonic and γ-bromosenecioic trimethylsilyl esters, with benzaldehyde is discussed.One-step reactions lead to a majority of α-substituted derivatives, while in two-step reactions, γ-substituted products are exclusively obtained.
- Bellassoued, M.,Gaudemar, M.,Borgi, A. El.,Baccar, B.
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p. 165 - 172
(2007/10/02)
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- N-Trimethylsilyl Imines: Applications to the Synthesis of β-Lactams
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Ester enolates and N-trimethylsilyl imines react to afford N-protio-β-lactams.The stereochemical course of the reaction depends on the ester enolate geometry.Therefore (E)-enolates give mainly cis β-lactams while (Z)-enolates give nearly equal mixtures of cis and trans β-lactams.The use of ethyl β-hydroxybutyrate as the ester component allows the preparation of β-lactams of potential use in carbapenem synthesis.The differences in the behavior of N-trimethylsilyl and N-aryl imines in ester-imine condensations are also discussed.
- Ha, Deok-Chan,Hart, David J.,Yang, Teng-Kuei
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p. 4819 - 4825
(2007/10/02)
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- Carbanions. 23. Cleavage of 1,2-Diphenylethane and Derivatives by Cs-K-Na Alloy. Cometitive Rates of Bond Scission
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The following hydrocarbons are cleaved at a C-C bond to allylic and or/benzylic cesium compounds within 2 h by Cs-K-Na alloy in THF at -75 deg C: meso-2,3-diphenylbutane, 2,3-dimethyl-2,3-diphenylbutane, 1,2,2-triphenylpropane, 4-phenyl-1-butene, bibenzyl, and eight o-,m-, or p-methyl derivatives of bibenzyl.Under the same conditions 2-methyl- and 3-methyl-4-phenyl-1-butene were partially cleaved, 4,4'-dimethylbibenzyl was only slightly cleaved, and 9,10-dihydrophenanthrene was not detectably cleaved, while 10,11-dihydro-5H-dibenzocycloheptene underwent alternative C-H bond cleavage.Under the present reaction conditions 4,4'-dimethylbibenzyl and 9,10-dihydrophenanthrene were converted largely to dianions.It is suggested that all of the compounds undergoing cleavage are converted to dianions prior to cleavage.From competitive experiments the rates of reductive cleavage of most of these hydrocarbons relative to bibenzyl have been measured at -75 deg C.The relative rates of cleavage of m- and p-methylderivatives of bibenzyl may be correlated with the relative equilibrium acidities of toluene, m-xylene, and p-xylene in a modified Hammett relationship.Cleavages of benzylic C-C bonds are believed to occur by way of a preferred transition-state geometry,7, which permits the ?* orbital of the bond undergoing cleavage to interact with the HOMO's of both aromatic rings.Compounds that cannot attain this transition-state geometry are cleaved slowly if at all.The variable effect upon reaction rate of methyl groups near the bond undergoing cleavage are discussed in terms of ground-state and transition-state atrain, solvation, and polarizability of methyl groups.According to labeling experiments (o-methylbenzyl)cesium undergoes ready intramolecular sigmatropic migration of hydrogen from the methyl group to the methylene group when warmed from -75 deg C to near room temperature.
- Grovenstein, Erling,Bhatti, Amjad M.,Quest, Dean E.,Sengupta, Dibyendu,VanDerveer, Don
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p. 6290 - 6299
(2007/10/02)
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- Microbial oxidation of α-allenic alcohols
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By microbial oxidation of α-allenic alcohols, α-allenic acids are formed.
- Bertrand,Ferre,Gil,Le Petit,Deveze
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p. 1711 - 1714
(2007/10/02)
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