TRANSITION-METAL-CATALYZED CHLORINE TRANSFER CYCLIZATIONS OF CARBON-CENTERED GLYCINE RADICALS - A NOVEL SYNTHETIC ROUTE TO CYCLIC ALPHA-AMINO-ACIDS

Copper(I)-catalyzed chlorine transfer radical cyclizations of several alpha-chloroglycine derivatives with a 3-alkenyl substituent at nitrog en are reported. These reactions proceed via 2-aza-5-alken-1-yl radica ls as intermediates which bear electron-withdrawing carbonyl substitue nts at the radical center and at nitrogen. These radicals can be consi dered as relatively stable captodative radicals, which are easily gene rated in the presence of Cu(bpy)Cl, but are reactive enough for olefin cyclization. The main products usually arise from 5-exo cyclization a nd are structurally interesting analogues of proline. An X-ray crystal structure of one of the cyclization products is presented.