Stereocontrol of 1,5-related stereocentres using an intermediate silyl group—the diastereoselectivity of nucleophilic attack on a double bond adjacent to a stereogenic centre carrying a silyl group
作者:Ian Fleming、Pranab Maiti、Chandrashekar Ramarao
DOI:10.1039/b305880h
日期:——
R-5-Methylcyclohex-2-enone 1 reacts successively with the phenyldimethylsilylzincate reagent and acetaldehyde to give with regiocontrol the aldols 7, dehydration of which creates the E-exocyclic double bond of the alpha,beta-unsaturated ketone 2. Conjugate addition of the ethylcuprate reagent to this compound takes place with high (96:4) selectivity in favour of the R stereoisomer 12, hydrolysis of
R-5-甲基环己-2-烯酮1与苯基二甲基甲硅烷基锌酸酯试剂和乙醛连续反应,通过区域控制得到羟醛7,其脱水产生α,β-不饱和酮2的E-外环双键。有利于R立体异构体12的高选择性(96:4)发生该化合物的铜cup酸乙酯试剂水解,得到(2R,3R,5S,2'R)-2-(but-2'-yl)- 3-二甲基(苯基)甲硅烷基-5-甲基环己酮3.该酮的肟肟在三甲基甲硅烷基三氟甲磺酸酯的存在下发生裂解,得到3R,7R,5E-3,7-二甲基非-5-腈4高度立体控制建立了1,5-立体链关系。相似的序列将4-甲基戊基戊酸酯加到烯酮2中,片段化后得到3R,