Regioselective Synthesis of 2,3,4- or 2,3,5-Trisubstituted Pyrroles via [3,3] or [1,3] Rearrangements of <i>O</i>-Vinyl Oximes
作者:Heng-Yen Wang、Daniel S. Mueller、Rachna M. Sachwani、Rachel Kapadia、Hannah N. Londino、Laura L. Anderson
DOI:10.1021/jo200061b
日期:2011.5.6
base. When enolization is favored, a [3,3] rearrangement followed by a Paal-Knorr cyclization provides a 2,3,4-trisubstituted pyrrole; when enolization is disfavored, a [1,3] rearrangement occurs prior to enolization to produce a 2,3,5-trisubstituted pyrrole after cyclization. Optimization and scope of the O-allyl oxime isomerization and subsequent pyrrole formation are discussed and mechanistic pathways
2,3,4-或2,3,5-三取代的吡咯的区域选择性合成分别通过O-乙烯基肟的[3,3]和[1,3]σ向重排实现。易于制备的O-烯丙基肟的铱催化异构化作用使得能够快速获得O-乙烯基肟。吡咯形成的区域选择性可以通过α-取代基的身份或通过添加胺碱来控制。当需要烯醇化时,先进行[3,3]重排,然后进行Paal-Knorr环化,即可得到2,3,4-三取代的吡咯;当烯醇化不利时,在烯醇化之前会发生[1,3]重排,从而在环化后产生2,3,5-三取代的吡咯。O的优化和范围讨论了烯丙基肟的异构化和随后吡咯的形成,并提出了机理。提供了选择带有β-酯O-烯丙基肟底物的[3,3]重排或[1,3]重排产物的条件。