Catalyst and Ring Size Effects on Periselectivity of Oxonium Ylide Rearrangements
作者:Fredrik P. Marmsäter、John A. Vanecko、F. G. West
DOI:10.1021/ol049493t
日期:2004.5.1
six-membered oxonium ylides. 4,5-Bis(benzyloxy) and 4-allyloxy-5-benzyloxy substrates 3a,b showed a large preference for rearrangement via the five-membered ylide under all conditions. However, a sharp divergence was seen with 5-allyloxy-4-benzyloxy substrate 3c, which underwent predominantly a [2,3]-shift to pyran 5c via the six-membered ylide with Cu(II) catalysis and a [1,2]-shift to furan 4c via
将重氮酮与Rh(II)或Cu(II)催化剂进行卡宾转移,以研究通过五元或六元氧代鎓叶立德进行重排的选择性。4,5-双(苄氧基)和4-烯丙氧基-5-苄氧基底物3a,b在所有条件下均显示出对通过五元内酯进行重排的较大偏好。但是,在5-烯丙氧基-4-苄氧基底物3c上观察到了明显的分歧,该底物主要通过具有Cu(II)催化作用的六元内酯和[1,2]发生[2,3]-转变为吡喃5c。通过具有Rh(II)催化的五元内立基转移至呋喃4c。