Reactions of fluoroalkanesulfonyl azides with carbocyclic β-keto esters: structural influence of dicarbonyl substrate on distribution of diazo and ring-contraction products

The diazo transfer reactions of fluoroalkanesulfonyl azides 1 with ethyl 2-oxocyclopentanecarboxylate 2, in the presence of triethylamine, give ring-opened diazo amido esters 3a–3d in high yields. Rhodium-catalyzed decompositions of these novel diazocarbonyl compounds 3 have been examined. The results show that β-hydride elimination by an intermediate carbene or rhodium-carbenoid is exclusively preferred, and the intramolecular cyclization onto the N-sulfonylcarbamoyl substituent does not take place. However, when fluoroalkanesulfonyl azides 1 react with ethyl 2-oxocyclohexanecarboxylate 5, the ring-contraction product cyclopentanecarboxylate 6 is formed as the only product.