Tuning of Vinylborane Dienophilicity. Optimization of Reactivity, Regioselectivity, endo-Stereoselectivity, and Reagent Stability
作者:Daniel A. Singleton、Jose P. Martinez、José V. Watson、Grace M. Ndip
DOI:10.1016/s0040-4020(01)90174-7
日期:1992.7
Diels-Alder reactions are compared. Vinyl-3,6-dimethylborepane was the most stable simple vinylborane examined, and appears to be indefinitely stable at 25°C. Surprisingly, trivinylborane is the most reactive, and reacts about 18 times faster than the vinyldialkylboranes with cyclopentadiene. Vinyl-9-BBN is the most regioselective dienophile, in keeping with principally steric control of regioselectivity
报告了一些乙烯基硼烷的简单合成,并比较了它们在Diels-Alder反应中的性质。乙烯基-3,6-二甲基硼烷是最稳定的简单乙烯基硼烷,在25°C下似乎无限稳定。出乎意料的是,三乙烯基硼烷是最活泼的,并且与乙烯基二烷基硼烷与环戊二烯的反应快约18倍。乙烯基-9-BBN是最具区域选择性的亲二烯体,与乙烯基硼烷的Diels-Alder反应中区域选择性的主要空间控制保持一致。所有的双亲物都显示出高内吞戊烯具有-立体选择性,而乙烯基3,6-二甲基环戊烷则显示出显着改善的环戊二烯立体选择性。通常,通过选择硼上的烷基取代基,可以优化乙烯基硼烷的反应性,区域选择性,内部立体选择性和稳定性。