Kaori Ando

Practical synthesis of Z-unsaturated esters by using a new Horner-Emmons reagent, ethyl diphenylphosphonoacetate

Abstract A new Horner-Emmons reagent, ethyl diphenylphosphonoacetate 1 was prepared from triethyl phosphonoacetate, PCl 5 , and phenol in 60% overall yield. Horner-Emmons reactions of 1 with aldehydes in the presence of Triton ® B or NaH in THF gave the Z -unsaturated esters in 89–93% selectivity in almost quantitative yields. Furthermore, 1 showed up to 99% Z -selectivity under Stills condition (KHMDS/18-crown-6).

Stereoselective reactions. XXI: Asymmetric alkylation of α-alkyl β-keto esters to α,α-dialkyl β-keto esters having either (R)- or (S)-chiral quaternary center depending on the solvent system

Abstract Asymmetric alkylation reaction of chiral enamines prepared from α-alkyl β-keto esters and ( S )-valine tert -butyl ester leading to either enantiomer is described. Lithiated chiral enamines can be alkylated with alkyl halides in a toluene solvent in the presence of HMPA to give, after hydrolysis, α,α-dialkyl β-keto esters in 70–99%ee. The reactions in the presence of THF, dioxolane, or trimethylamine, instead of HMPA, afford the corresponding antipodes with enantiomeric purities of 44–92%ee. The present method provides a procedure for the synthesis of both enantiomers of α,α-dialkyl β-keto esters in high enantiomeric purities starting from the same chiral enamines.

Asymmetric Michael reaction of α-alkyl β-keto esters via chiral enamines

Summary Depending on the combination of solvents and additives, Michael reaction of chiral lithioenamines generated from 1a,b with di- tert -butyl methylenemalonate ( 2 ) affords, after hydrolysis, either enantiomers of α,α -disubstituted β-keto esters ( 3,4 ) in high enantiomeric excess.

Chlorotrimethylsilane promoted asymmetric Michael reaction of chiral enamines of α-alkyl β-keto esters

Abstract By the promotion of chlorotrimethylsilane, asymmetric Michael reaction of the chiral enamines ( 2 ) of α-alkyl β-keto esters ( 1 ) with methyl vinyl ketone and ethyl acrylate proceeded to afford, after hydrolysis, either enantiomer of the corresponding adducts ( 4 ) in a good enantioselectivity.

Heteroaromatic-fused 3-Sulfolenes

This review deals with our recent works on the preparation of heteroaromatic-fused 3-sulfolenes (5) and their chemistry, especially Diels-Alder reactions with several dienophiles under thermal or high pressure conditions. Related chemistry of the positional isomers (6) is also reviewed

Factors controlling the diastereoface selectivity in the complementary asymmetric alkylation of α-alkyl β-keto esters

Abstract Complementary asymmetric alkylation reaction of the lithioenamine derived from 2-methoxycarbonylcyclohexanone and ( S )-valine tert -butyl ester was examined by employing the various electron pair donating additives in a toluene solvent, in order to clarify the factors controlling the diastereoface selectivity.

Thermal reactions of (2,4,6-tri-butylphenyl)phosphonous dichloride and its derivatives; formation of 2,3-dihydro-1h-phosphinodes

Abstract 2,3-Dihydro-1H-phosphindole derivatives were obtained from thermal reactions of (2,4,6-tri-tert-butylphenyl)phosphonous dichloride in refluxing toluene, probably through cyclization involving phosphorus radicals with an adjacent methyl of o-tert-butyl groups.

Z-selective intramolecular Horner-Wadsworth-Emmons reaction for the synthesis of macrocyclic lactones.

When the substrates (ArO)(2)P(O)CH(2)CO(2)---CHO (Ar = Ph, o-t-BuPh) were added to a THF solution containing 3 equiv of NaH at 0 degrees C or NaI-DBU at rt over 1-10 h, the intramolecular Horner-Wadsworth-Emmons reaction proceeded efficiently to give the 12-18-membered-ring lactones in 69-93% yields with 89-100% Z selectivity. On the other hand, (EtO)(2)P(O)CH(2)CO(2)---CHO gave the 13-18-membered-ring lactones in 52-82% yields with 89-99% E selectivity using LiCl-DBU in MeCN or THF.

Highly E-selective solvent-free Horner–Wadsworth–Emmons reaction catalyzed by DBU

The solvent-free Horner–Wadsworth–Emmons reaction of triethyl phosphonoacetate with a variety of aldehydes was catalyzed by DBU in the presence of K2CO3 to give E-α,β-unsaturated esters highly selectively (99 : 1 for most of the reactions). The reaction with ketones gave trisubstituted olefins with good to high E-selectivity by DBU-Cs2CO3.

Ab initio molecular orbital study on the mechanism of amide hydrolysis dependent on leaving groups

Abstract The alkaline hydrolysis of amides, N-methyl acetamide 1, acetanilide 2, and N-acetyl imidazole 3, was investigated by use of ab initio molecular orbital calculations. A detailed analysis was performed for two possible mechanisms, Path 1 and 2. Path 1, similar to ester hydrolysis, releases CH3COOH and RNH whereas Path 2 contains the RNH group that extracts the H atom from the OH fragment in the tetrahedral intermediate. In this mechanism, carboxylate ion and an amine directly form. It was ascertained that Path 2 is a better route to decompose the TD intermediate than Path 1 for 1 and 2 in the gas phase. The stability of the leaving group RNH determines which route, Path 1 or 2, is preferred in the gas phase. The solvent effect was estimated for the two mechanisms by using the SCRF calculations of the IPCM model.