Facile Construction of Spirocyclopropanated Bi-, Tri- and Tetracyclic Skeletons by Novel Cascades Involving Intra- and Intermolecular Heck Reactions of 2-Bromo-1,6-enynes and Bicyclopropylidene
作者:Michael Schelper、Armin de Meijere
DOI:10.1002/ejoc.200400668
日期:2005.2
elevated temperatures (120−140 °C) the initially formed tetraenes underwent 6π-electrocyclization to give spiro[cyclopropane-1,4′-bicylo[4.3.0]-1(6),2-dienes] 21-R, 22-R and 23-R. This novel class of spirocyclopropanated oligocycles is also accessible by a one-pot protocol. The highest yields for both the tetraenes and bicyclo[4.3.0]nonadiene and its heteroanalogues were obtained with bulky substituents
radical reductive cyclization of 1,6-enynes. A strategy involving in situ iodination/radical cyclization/silyl radical-mediated halogenatom transfer/hydrogenatom transfer for the synthesis of functionalized pyrrolidines has been proposed. Using this halogen-atom abstraction protocol, 1,6-enynes with various vinyl halides including inert fluorides, chlorides, and reactive bromides could be transformed