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DABCO-Catalyzed 1,4-Bromolactonization of Conjugated Enynes: Highly Stereoselective Formation of a Stereogenic Center and an Axially Chiral Allene

2009; American Chemical Society; Volume: 131; Issue: 11 Linguagem: Inglês

10.1021/ja8099008

1943-2984

Wen Zhang, Hua‐Dong Xu, Hui Xu, Weiping Tang,

Catalytic C–H Functionalization Methods

A DABCO-catalyzed highly regio- and stereoselective syn-1,4-bromolactonization of conjugated enynes was discovered. The 1,4-addition occurred selectively over 1,2-addition for most enynes. In contrast to anti 1,2-addition to alkenes, where two adjacent stereogenic centers are created, 1,4-addition across conjugated enynes can produce a stereogenic center and an axially chiral allene simultaneously. Enynes with Z and E configurations yielded products with complementary stereochemistries at the newly generated stereogenic center and axially chiral allene. Di-, tri-, or even tetrasubstituted allenes together with lactones can be efficiently and selectively prepared from this enyne bromolactonization reaction.