Synthesis of .gamma.- and .delta.-lactones by free-radical annelation of Se-phenyl selenocarbonates
摘要:
A general method for the synthesis of gamma- and delta-lactones through the intramolecular addition of alkoxycarbonyl radicals, formed by reaction of Se-phenylselenocarbonates with n-Bu3SnH, onto carbon-carbon multiple bonds is described. This free-radical cyclization is characterized by high regioselectivity favoring exo addition and by a high ratio of cyclization to reduction. Monocyclic, fused bicyclic, and spirocyclic lactones are formed in good to excellent yield. Use of allyltri-n-butyltin as a chain-transfer agent in the place of n-Bu3SnH affords the corresponding 3-butenyl lactones.
Formal Alkyne Aza-Prins Cyclization: Gold(I)-Catalyzed Cycloisomerization of Mixed N,O-Acetals Generated from Homopropargylic Amines to Highly Substituted Piperidines
作者:Cheoljae Kim、Hyo Jin Bae、Ji Hyung Lee、Wook Jeong、Haejin Kim、Vasu Sampath、Young Ho Rhee
DOI:10.1021/ja906744r
日期:2009.10.21
cycloisomerization to access highly substituted piperidines has been developed. By combining a conceptually new way of generating iminium ions using cationic gold(I) complexes and an efficient cyclization reaction that can minimize a potentially competing aza-Cope rearrangement, the proposed reaction successfully circumvents a long-standing problem in the classical aza-Prins reaction. Synthetic utility of the catalytic