A novel enantioselectivebromolactonization of α,β-unsaturated ketones using bifunctional amino-urea catalysts has been developed. The scope of the reaction is evidenced by 23 examples of halolactones bearing various functionalities with up to 99% yield and 99:1 er. Unlike typical urea catalysts that require electron-deficient substituents to enhance the hydrogen bond strength, it is interesting to
The apple never falls far from the tree: S‐alkylthiocarbamate 1 (see scheme, NBP=N‐bromophthalimide) was prepared in high yield through a synthetic sequence involving a Newman–Kwart rearrangement of the corresponding O‐alkylthiocarbamates. Compound 1 was used to catalyze bromolactonization, thus providing enantioenriched δ‐lactones in excellent yield and enantioselectivity.
A direct and efficient method for the preparation of 5-benzoyldihydro-2(3H)-furanones was realized by cyclization of 4-benzoylbutyric acids in the presence of phenyliodine(III) triflate.
A novel approach for the synthesis of β-keto esters: one-pot reaction of carboxylic acids with chlorosulfonyl isocyanate
作者:Ufuk Atmaca
DOI:10.24820/ark.5550190.p011.209
日期:——
esters were synthesized by direct carboxylation of various 4and 5-oxo-carboxylic acid derivatives in the presence of chlorosulfonyl isocyanate in excellent yield under mild conditions. Additionally, optimization conditions were examined for synthesis β-keto esters. Finally, it has been found that trifluoroacetic acid is efficient in DCM under optimized conditions. This efficient one-pot novel method