The 1,4-addition of organotitaniumatecomplexes to enones by nickel catalysis is reported. With a methyltitanium atecomplex good yields of conjugate addition to stericallyhinderedenones are achieved. Phenyltitanium atecomplexes react with less sterically encumbered enones to the 1,4-addition products in moderate to high yields.
Nickel acetylacetonate is an efficient catalyst for the 1,4-addition of trimethylaluminum to α,β-unsaturated ketones. The reaction is strongly solvent dependent and gives best results in tetrahydrofuran or ethyl acetate. The reaction is especially useful for the nucleophilic 1,4-methyl transfer to sterically hindered enones. A β-cuparenone synthesis via conjugate methyl group addition to an enone precursor is described.
作者:Bruce H Lipshutz、Paul Mollard、Craig Lindsley、Virginia Chang
DOI:10.1016/s0040-4039(97)00239-6
日期:1997.3
Conversion of aldehydes and ketones to 1,3-dioxanes with 2-trimethylsilyl-1,3-propanediol affords carbonyl-protected products, ultimately susceptible to unmasking with LiBF4 in THF. (C) 1997 Elsevier Science Ltd.
A sequential stereocontrolled cyclopropane ring formation and semi-pinacol rearrangement
作者:Charles M. Marson、Catriona A. Oare、Jane McGregor、Timothy Walsgrove、Trevor J. Grinter、Harry Adams
DOI:10.1016/s0040-4039(02)02511-x
日期:2003.1
Treatment of an unsaturated 2,3-epoxy alcohol with SnBr4 leads to a stereoselective formation of a cyclopropane ring, and an α-ketol unit as part of a subsequent ring expansion.