Intramolecular C-H Functionalization of alpha-Alkyl-alpha-diazoesters towards the Synthesis of Lactones

Intramolecular C-H functionalization was achieved using rhodium-catalysis with alpha-alkyl-alpha-diazoesters. Dirhodium tetratriphenylacetate (Rh2(TPA)4), a sterically bulky achiral catalyst was found to enable the formation of lactones. Alkyl gamma-lactones were synthesized in excellent yields and diastereoselectivity, and a diverse array of disubstituted lactones (gamma-, delta-, epsilon-) were synthesized with good yields and diastereoselectivity. This chemistry was extended to intramolecular C-H insertion in late-stage functionalization with an excellent regio- and diastereoselectivity.