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.
Alkylation de quelques composés carbonylés par des groupes tertiaires. Utilisation de la réaction de friedel-crafts dans la synthèse d'ésters
作者:Claude Lion、Jacques-Emile Dubois
DOI:10.1016/s0040-4020(01)92017-4
日期:1981.1
t-Alkylation of carboxylic esters via their ketene alkyltrimethylsilyl acetals by the Friedal-Crafts reaction allows the synthesis of new highly hindered compounds. A new route using sodium amide in dimethoxyethane, for the preparation of trimethylsilylenol ethers of ketones, is described. The α-t-butylation of these compounds permits the synthesis of new crowded pentasubstituted ketones. The limits
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