Accurate determinations of the extent to which the SE2? reactions of allyl-, allenyl- and propargylsilanes are stereospecifically anti
作者:Michael J. C. Buckle、Ian Fleming、Salvador Gil、Kah Ling Christine Pang
DOI:10.1039/b313446f
日期:——
propargylsilane (R)-1,3-bis(trimethylsilyl)but-1-yne (er >99.7:0.3) was prepared from the sultam 13, by removal of the chiral auxiliary with lithium ethoxide, reduction of the ethyl ester to give (R)-3-trimethylsilylbutanal 60, enol triflate formation, beta-elimination and C-silylation. The propargylsilane reacted with 2,4-dinitrobenzaldehyde in the presence of titanium tetrachloride to give the allenes, 1-(2,4
烯丙基硅烷(R)-E-和(R)-Z-4-三甲基甲硅烷基戊-2-烯16基本上以对映体和几何纯态(er> 99.95:0.05,E:Z和Z:E> 99.95:0.05),依次将共轭二甲基铜锂添加到N-[((E)-3'-三甲基甲硅烷基丙烯酰基]-(7S)-10,10-二甲基-4-氮杂-5-硫代三环[5.2.1 .0 (3,7)]癸烷5,5-二氧化物13,得到N-[(E)-(3'R)-3'-三甲基甲硅烷基丁酰基]-(7S)-10,10-二甲基-4-氮杂-5 -硫代三环[5.2.1.0(3,7)]癸烷5,5-二氧化物,用溴镁苄氧化物除去手性助剂,与乙醛进行醛醇缩合反应,并脱羧消除,得到Z-或E-异构体。E-和Z-烯丙基硅烷16都与金刚烷基阳离子反应,得到E-和Z-4-金刚烷基戊-2-烯的混合物17。E-烯丙基硅烷产生的E-和Z-产物的比率为40:60,Z-烯丙基硅烷产生的E-和Z-产物的比率为99.8:0