aldol reactions in water using a catalytic amount of diarylborinic acid have been developed. The reactions proceeded smoothly in the presence of a small amount of an anionic surfactant and a Brønsted acid. Water was the most suitable solvent, and organic solvents such as ether and dichloromethane were ineffective in this system. Use of bis(4-trifluoromethylphenyl)borinic acid gave high catalytic activity
aromatic aldehydes and silyl enol ethers in benzene as the solvent. The reactions occur with high simple diastereoselectivity and, when R¹ is chiral, with high facial diastereoselectivity. Under similar conditions, but in acetonitrile rather than benzene as the preferred solvent, the Paternò-Büchi reaction of N-acylenamines (enamides) gives the corresponding protected 3-aminooxetanes. The cis-products
The trimethylsilyl triflate mediated reaction of benzyl diphenylphosphinate with allyltrimethylsilane or trimethylsilyl enolate afforded the corresponding cross-coupling products in good yields.
Stereoselective photocycloaddition of silyl enol ethers to aldehydes. Configurational control of three stereogenic centers in oxetanes
作者:Thorsten Bach
DOI:10.1016/s0040-4039(00)78199-8
日期:1994.8
The photocycloaddition of unsymmetrically substituted alkenes to an aldehyde leads to eight possible isomeric oxetanes. In sharp contrast to most other substrates, silyl enolethers 1 which bear a vinylic β-substituent favor only a single stereo- and regioisomer 2 as major product of this reaction.