- Carbene-catalyzed enal γ-carbon addition to α-ketophosphonates for enantioselective access to bioactive 2-pyranylphosphonates
-
A carbene-catalyzed enantioselective [4+2] cycloaddition reaction between α,β-unsaturated aldehydes and α-ketophosphonates is developed. The reaction affords chiral 2-pyranylphosphonates with excellent enantioselectivities. The optically enriched phosphonate products bear multiple functional groups, including unsaturated lactone and phosphonate moieties that often lead to unique bio-activities. Preliminary studies show that the products from our reactions exhibit anti-bacterial (X. oryzae pv. oryzae) and anti-viral (Tobacco Mosaic Virus) activities for potential use in plant protection.
- Sun, Jun,He, Fangcheng,Wang, Zhongyao,Pan, Dingwu,Zheng, Pengcheng,Mou, Chengli,Jin, Zhichao,Chi, Yonggui Robin
-
supporting information
p. 6040 - 6043
(2018/06/18)
-
- Highly enantioselective aerobic oxidation of α-hydroxyphosphonates catalyzed by chiral vanadyl(V) methoxides bearing N-salicylidene-α- aminocarboxylates
-
An unprecedented vanadyl(V) methoxide complex 4 derived from 3,5-dibromo-N-salicylidene-l-tert-leucinate enables highly enantioselective aerobic oxidations of α-hydroxyphosphonates at ambient temperature with selectivity factors ranging from 3 to >99. Cop
- Pawar, Vijay D.,Bettigeri, Sampada,Weng, Shiue-Shien,Kao, Jun-Qi,Chen, Chien-Tien
-
p. 6308 - 6309
(2007/10/03)
-
- The preparation of acyl phosphonates by the heterogeneous oxidation of 1-hydroxy phosphonates
-
The oxidation of hydroxy phosphonates to acyl phosphonates using three heterogeneous systems, MnO2, KMnO4 and CrO2, was investigated. The best results were obtained with CrO2 in refluxing acetofinitrile.
- Liao, Yihua,Shabany, Hossein,Spilling, Christopher D.
-
p. 8389 - 8392
(2007/10/03)
-
- Acylphosphonate hemiketals - Formation rate and equilibrium. The electron-withdrawing effect of dimethoxyphosphinyl group
-
Examination of alcoholic solutions of dimethyl acetylphosphonate (1) and dimethyl benzoylphosphonate (2) by 31P NMR spectroscopy reveals the presence of considerable amounts of hemiketals. Because of the great difference between the 31P chemical shifts of acylphosphonates (ca. 0 ppm) and their hemiketals (17-21 ppm), 31P NMR spectroscopy is a uniquely suitable method for studying the rates and equilibria of hemiketal formation of acylphosphonates with different alcohols. The equilibrium constants Kf, K′f (K′f = Kf[ROH]), pseudo-first-order rate constants k′f, the second order rate constants, kf for hemiketal formation from dimethyl acetylphosphonate with various alcohols, as well as the reverse reaction rate constants, kr to starting materials, were determined. The kinetic isotope effect of 2.8 for the forward reaction kf (EtOH addition) and the backward reaction kr indicates a general catalysis pathway. On the other hand, the calculated values of the enthalpies of activation ΔH? = 10.37 kcal mol-1 (forward), ΔH? = 13.66 kcal mol-1 (backward) and the entropies of activation, ΔS? = -17.25 cal mol-1 K-1 (forward), ΔS? = -9.82 cal mol-1 K-1 (backward) are not in accord with high molecularity of the reaction (1 cal = 4.184 J). Our analysis led to the conclusion that this is probably due to the fact that the transition state is mainly reactant-like with the development of only limited extent of bond formation. Various plausible reaction pathways for hemiketal formation are discussed. In addition, we have calculated the value of 2.65 σ* for the P(O)(OMe)2 group based on proton affinity obtained from heats of formation (ΔHf) of applying the MNDO techniques. The following linear correlation between pKa values and PA values of hemiketals of the form (Me)(R)C(OH)(OCH2X) was developed: pKa = PA - 356.58 + 9.18 [σ*(Me) + σ*(R) + 0.2σ*(X)].
- Katzhendler, Jehoshua,Ringel, Israel,Karaman, Rafik,Zaher, Hisham,Breuer, Eli
-
p. 341 - 349
(2007/10/03)
-
- Photochemistry of Matrix-Isolated (α-Diazobenzyl)phosphonate. Observation and Reactions of Phosphonylphenylcarbene, Phosphonyl Phenyl Ketone Oxide, and Phenylphosphonyldioxirane
-
Photolysis of dimethyl α-diazobenzylphosphonate (1) in an Ar matrix at 10 K resulted in the appearance of new absorption bands at 1268, 788, and 536 cm-1, attributable to the carbene 2.The assignment was based on the observation that the new ab
- Tomioka, Hideo,Komatsu, Kazunori,Shimizu, Masayoshi
-
p. 6216 - 6222
(2007/10/02)
-
- PHOSPHORIC-CARBOXYLIC IMIDES. III. THE BENZOYLATION OF N-METHYLDIETHYLPHOSPHORAMIDATE AND RELATED ANIONS
-
The synthetic route to mixed phosphoric-carboxylic imides (1) via the N-acylation of phosphoramidates was investigated.The reaction of PhC(O)X(X = Br, Cl, F) with conjugate base of (EtO)2P(O)NHMe (2) yields three products: PhCO2Et (3), PhC(O)NHMe (4) and (PHCO)2NMe (5). (4) and (5) are formed via the initial rapid formation of (1), while (3) results from the ElcB raction of (2).The attack of various nucleophilic species at mixed imide (1) was studied, and the possible mechanisms of the P-N bond cleavage, followed by the transfer of nitrogen from phosphoryl to the carbonyl centre, are discussed.
- Hendrickse, Theodore F.,Mizrahi, Valerie,Modro, Tomasz A.
-
-