1069-54-1Relevant articles and documents
An Enantioconvergent and Concise Synthesis of Lasonolide A
Yang, Lin,Lin, Zuming,Shao, Shunjie,Zhao, Qian,Hong, Ran
, p. 16200 - 16204 (2018)
Efficient access to medicinally significant natural products is an essential basis for the development of pharmaceuticals. The limited availability of marine natural products impedes broad biological evaluation. Despite several elegant syntheses of (?)-lasonolide A having been reported, a practical synthesis of this potent anticancer polyketide remains elusive. Based on the application of borane as a traceless protecting group and the development of an unprecedented bissulfone reagent for Julia olefination, (?)-lasonolide A was assembled in an enantioconvergent manner through the application of stereoselective hydroboration, allylation, and oxidation. This concise route may provide a realistic solution for accessing derivatives and analogues.
Short-route synthesis of (3E,5Z)-tetradecadienoic acid (megatomic acid), the sex attractant of the black carpet beetle
Yadav,Reddy,Ramalingam
, p. 223 - 225 (2001)
A new and expeditious route to (3E,5Z)-3,5-tetradecadienoic acid (megatomic acid), the sex attractant of the black carpet beetle Attagenus megatoma (Fabricius), is reported which proceeds with 97% stereoselectivity; Cadiot-Chodkiewicz cross-coupling of 1-decyne and 4-bromo-3-butyn-1-ol in the presence of CuCl, followed by stereoselective reductions and Jones oxidation, gives the target molecule, with the synthetic pheromone showing a positive electrophysiological response.
Development and Mechanistic Interrogation of Interrupted Chain-Walking in the Enantioselective Relay Heck Reaction
Ross, Sean P.,Rahman, Ajara A.,Sigman, Matthew S.
, p. 10516 - 10525 (2020)
The formation of alkyl-palladium complexes via the nucleopalladation of alkenes is the entry point for a wide range of diverse reactions. One possibility is that the intermediate alkyl-Pd complexes can undergo a "chain-walking"event, to allow for remote functionalization through various termination processes. However, there are few methods to selectively interrupt the chain-walking process at a prescribed location. Herein, we demonstrate that a variety of homoallylic protected amines undergo an interrupted enantioselective relay Heck reaction to give enantioenriched allylic amine products. The selectivity of this process can be diverted to exclusively yield the ene-amide products by virtue of changing the nature of the amine protecting group. To rationalize this observation, we combine experiment and computation to investigate the mechanism of the chain-walking process and termination events. Isotopic labeling experiments and the computed reaction pathways suggest that the system is likely under thermodynamic control, with the selectivity being driven by the relative stability of intermediates encountered during chain-walking. These results illustrate that the chain-walking of alkyl-palladium complexes can be controlled through the alteration of thermodynamic processes and provides a roadmap for exploiting these processes in future reaction development.
Hydrovinylation of Norbornene. Ligand-Dependent Selectivity and Asymmetric Variations
Kumareswaran, Ramaiah,Nandi, Malay,RajanBabu
, p. 4345 - 4348 (2003)
(Equation presented) Norbornene undergoes Ni-catalyzed (1-2 mol% allylnickel bromide/phosphine/NaBARF or AgSbF6, 1 bar ethylene, -50°C) hydrovinylation (>97% yield), giving either a 1:1 or a 2:1 (norbornene/ethylene) adduct depending on the size of the phosphine. Use of binaphthol-derived phosphoramidite ligand results in up to 80% ee for the 1:1 adduct. The course of the reaction is highly dependent on the ligand (size and configuration of the appendages) and the counteranion present.
Stereodivergent synthesis of functionalized tetrahydropyrans accelerated by mechanism-based allylboration and bioinspired oxa-michael cyclization
Yang, Lin,Lin, Zuming,Huang, Sha-Hua,Hong, Ran
, p. 6280 - 6284 (2016)
A stereodivergent strategy enabled by bioinspired oxa-Michael cyclization was developed for the synthesis of functionalized tetrahydropyrans on the basis of the inherent symmetry in 1,3-diols, the symmetries of which were tunable by stereoselective hydroboration of an allene with a variety of alkylborane reagents and subsequent allylation of an aldehyde. The mechanism-based utilization of monoalkyl borane in the hydroboration and allylation cascade is unprecedented. Symmetry breakdown: The thermodynamic and kinetic hydroboration of allenes and subsequent allylboration provide a key stereodefinable module with a latent symmetry. Following a deprotection/chain elongation/oxa-Michael cyclization sequence, the stereocogeners of highly functionalized tetrahydropyrans were synthesized for rapid access to structural motifs found in bioactive polyketides.
An epoxidation approach to a chiral lactone: Application of the Shi epoxidation
Ager, David J.,Anderson, Ken,Oblinger, Eric,Shi, Yian,Vanderroest, James
, p. 44 - 51 (2007)
The large-scale epoxidation of the alkene 7 with the organo-catalyst, Epoxone (10), and Oxone as the oxidant is described. This is the first large-scale application of the Shi epoxidation methodology. The large-scale preparation of the catalyst 10 is also described. The potassium salt of the unsaturated acid precursor 7 was prepared by a Suzuki coupling from 3-fluorobenzyl chloride and the vinylborane 8 derived from 4-pentynoic acid.
Extension of Pd-Mediated One-Pot Ketone Synthesis to Macrocyclization: Application to a New Convergent Synthesis of Eribulin
Lee, Jung Hwa,Li, Zhanjie,Osawa, Ayumi,Kishi, Yoshito
, p. 16248 - 16251 (2016)
Recently reported Pd-mediated one-pot ketone synthesis from an unactivated alkyl bromide and a thioester has been extended to a macrocyclic ketone synthesis. In situ generation of alkylzinc halide via single electron transfer (SET), using NbCpCl4 and CrCl3, was the key for the success of macrocyclization. A new convergent synthesis of eribulin has been achieved, using (1) catalytic asymmetric Ni/Cr-mediated coupling to form the C19-C20 bond, (2) base-induced cyclization to form the methylenetetrahydrofuran ring, and (3) Pd-mediated one-pot ketone synthesis to form the macrocyclic ketone.
Requirements for Lewis Acid-Mediated Capture and N-N Bond Cleavage of Hydrazine at Iron
Kiernicki, John J.,Zeller, Matthias,Szymczak, Nathaniel K.
, p. 1147 - 1154 (2019)
An iron complex bearing a pyridine(dicarbene) pincer was designed to probe the requirements of Lewis acid-enabled N2H4 capture and subsequent N-N bond cleavage. Appended boron Lewis acids were installed by two methods to circumvent the incompatibilities associated with Lewis acid/base quenching of free carbenes and boranes. N2H4 capture by borane Lewis acids is dependent on both the Lewis acidity and the steric profile about boron. A substitutionally inert primary coordination sphere at iron prevents an Fe-N2H4 interaction as well as N-N bond homolysis upon reduction.
Molecular addition compounds. 13. N,N-diisopropyl-n-isobutylamine-borane: The first highly reactive trialkylamine-borane reagent for hydroborations
Brown, Herbert C.
, p. 1310 - 1317 (1999)
N,N-Diisopropyl-N-isobutylamine (1) forms a stable liquid borane adduct (4.7 M in BH3), when diborane is bubbled into the neat amine. The adduct thus formed is stable indefinitely at room temperature under an inert atmosphere. Hydroboration studies with this new, highly reactive amine-borane adduct, H3B:NPri2Bui (2) and representative olefins, such as 1-hexene, styrene, β-pinene, cyclopentene, norbornene, cyclohexene, 2-methyl-2-butene, α-pinene, and 2,3-dimethyl-2-butene, were carried out at room temperature (22 ± 3°C) in selected solvents, tetrahydrofuran, dioxane, tert-butyl methyl ether, n-pentane, and dichloromethane. The reactions are faster in dioxane and n-pentane, requiring ～2 h for the hydroboration of simple, unhindered olefins to the trialkylborane stage.
First synthesis of both 1-aryl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles and 1-aryl-4-[(Z)-1-(trimethylsilyl)alk-1-enyl]-1H-1,2,3-triazoles: assembly of π-extended 1,2,3-triazoles using a cross-coupling/click reaction sequence
Oikawa, Asuka,Kindaichi, Gan,Shimotori, Yasutaka,Hoshi, Masayuki
, p. 4205 - 4213 (2016)
A practical and general synthetic approach to a series of π-extended 1,2,3-triazoles with both aryl and alkenyl moieties on the triazole ring is described. Synthesis of 1-aryl-4-[(E)-alk-1-enyl]-1H-1,2,3-triazoles can be achieved by the click reaction between terminal conjugated (E)-enynes, prepared by copper-mediated cross-coupling reaction of (E)-alk-1-enyldisiamylboranes with (trimethylsilyl)ethynyl bromide, and aryl azides, prepared from arylboronic acids and sodium azide in another flask and employed for the following click reaction without any purification. 1-Aryl-4-[(Z)-1-(trimethylsilyl)alk-1-enyl]-1H-1,2,3-triazoles can be also synthesized by a sequential three-step reaction, which involves copper-mediated cross-coupling reaction of (Z)-1-(trimethylsilyl)alk-1-enyldicyclohexylboranes with (trimethylsilyl)ethynyl bromide to form (Z)-1,3-bis(trimethylsilyl)alk-3-en-1-ynes, deprotection of the trimethylsilyl group on the alkynyl carbon atom to generate (Z)-3-(trimethylsilyl)alk-3-en-1-ynes and click reaction with aryl azides prepared in the same manner as described above. Both synthetic routes are tolerant of a wide range of functional groups with moderate to good yields.
