Straightforward Asymmetric Entry to Highly Functionalized Medium-Sized Rings Fused to β-Lactams via Chemo- and Stereocontrolled Divergent Radical Cyclization of Baylis−Hillman Adducts Derived from 4-Oxoazetidine-2-carbaldehydes
- 2 February 2001
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 66 (5) , 1612-1620
- https://doi.org/10.1021/jo005715z
Abstract
DABCO promoted reactions of various activated vinyl systems with optically pure 4-oxoazetidine-2-carbaldehydes 1 gave rise to Baylis−Hillman adducts 3 with excellent syn stereoselectivities, without detectable racemization. Products 3 are used for the asymmetric preparation of unusual 2-azetidinones fused to medium-sized rings via chemo- and stereocontrolled divergent radical cyclization. The formation of bicyclic β-lactams 4−6 could be rationalized through a tandem radical Michael addition/endo cyclization or a tandem radical addition/Michael addition, depending on the electronic nature of the radical promoter.Keywords
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