Highly Stereo- and Regioselective Formation of 2-Oxazolone Telomers, Potential Synthetic Intermediates for Amino Sugars

Free radical initiated reaction of 3-acyl-2-oxazolones proceeds smoothly in polyhalomethanes, which function as telogens, to give type 3 telomers of synthetic potential with high regio- and stereoselectivity, while the 3-alkyl derivatives failed to give such polyfunctional products. This particular telomerization can be controlled exclusively in the trans “head-to-tail” addition mode, as elucidated by and ¹³C NMR and X-ray analysis of the products. Thus, the 3-benzoyl heterocycle 7 gave trans-4-chloro-5-(trichloromethyl)-2-oxazolidone (8) as a sole 1:1 adduct and two trans isomers of 4′-chlorc-5-(trichloromethyl)[4,5′-bioxazolidinyl]-2,2′-dione (9a,b) as 2:1 telomers. Some characteristic reactions of the telomers are described.