Highly diastereoselective alkylation, acylation and aldol condensation of cis- and trans-(N-acyloyl)hexahydrobenzoxazolidin-2-ones
作者:Cecilia Anaya de Parrodi、Angel Clara-Sosa、Lydia Pérez、Leticia Quintero、Virginia Marañón、Rubén A. Toscano、Judit A. Aviña、Susana Rojas-Lima、Eusebio Juaristi
DOI:10.1016/s0957-4166(00)00492-4
日期:2001.2
rationalized in terms of a Zimmerman–Traxler transition state, with a (Z)-configured enolate where boron is coordinated to the aldehyde carbonyl rather than the oxazolidinone carbonyl. Substrate 2a was also reacted with acyl chlorides via the sodium enolate (NaHMDS). The effect of reaction conditions on O- versus C-acylation, as well as the influence of solvent and additives on diastereoselectivity, are
探索了六氢苯并恶唑烷酮1a – d作为手性助剂的潜力。1a - d,2a - d和3a - d的N-酰化后,通过NaHMDS处理产生的相应烯醇钠进行甲基化和苄基化。观察到非对映选择性为98%或更高。通过与2-苄基-1-丙醇的化学相关性,建立了新创建的立体异构中心的绝对构型。立体化学结果与从(Z)-构型的烯醇盐,钠阳离子由底物的两个羰基氧配位。顺式-和反式- ñ -丙酰基衍生物2A - d用卜处理2 BOTf / ET 3 N到得到烯醇化物dialkylboron 6A - d,然后将其与乙醛和苯甲醛反应。1 H和13 C NMR分析显示单一非对映体醛醇加成产物,其相对的配置被确定为形成顺从测量3 Ĵ H(2')/ H(3')耦合常数,其绝对构型由X射线晶体学分析确定。结果是根据Zimmerman-Traxler过渡态进行合理化的,其中具有(Z)构型的烯醇化物,其中硼与羰基醛而不是恶唑烷酮羰