Stereoselective Radical Tandem Cyclohydrostannation of Optically Active Di-unsaturated Esters of TADDOL
作者:Darío C. Gerbino、Liliana C. Koll、Sandra D. Mandolesi、Julio C. Podestá
DOI:10.1021/om700693p
日期:2008.2.1
diastereoisomers, respectively, the addition of triphenyltin hydride to TADDOL disubstituted acrylates yields only four out of the 16 possible stereoisomers. The observed high stereoselectivity is consistent with the radical tandem cyclohydrostannation mechanism proposed. Only in the case of the hydrostannation of TADDOL diacrylate with trimethyl- and triphenyltin hydrides could the diastereoisomers obtained in
本文报道了三有机锡氢化物R 3自由基加成研究的结果。SnH(R = Me,n-Bu,Ph; Neophyl),形成四个TADDOL不饱和二酯。发现这些反应导致高产率的环氢化锡的产物。还发现,虽然将这些氢化物添加到TADDOL二丙烯酸酯和TADDOL二甲基丙烯酸酯中分别导致了两种和四种环十一烷非对映异构体的预期混合物,但是将氢化三苯锡添加到TADDOL二取代丙烯酸酯中却只产生了16种可能的立体异构体中的四种。观察到的高立体选择性与提出的自由基串联环氢化锡机理是一致的。只有在TADDOL二丙烯酸酯与三甲基和三苯基锡氢化物加氢锡的情况下,才能获得更高比例的非对映异构体(5a和8a)以纯净形式隔离。大环内酯5a和8a的随后还原(氢化铝锂)以高收率得到相应的旋光性二醇26和27。给出了全部1 H,13 C和119 Sn NMR数据。