Iterative One-Carbon\nHomologation of Unmodified Carboxylic\nAcids

The one-carbon homologation of carboxylic acids is a\nvaluable route\nto construct families of homologues, which play fundamental roles\nin chemistry and biology. However, known procedures are based on multistep\nsequences, use harsh conditions or are limited in scope. Thus, almost\na century after the discovery of the original Arndt–Eistert\nhomologation sequence, a general method to directly convert carboxylic\nacids into their corresponding homologues remains elusive. Exploiting\nthe photoredox reactivity of nitroethylene, we disclose a practical\nvisible-light-induced homologation of unmodified carboxylic acids.\nIterations of the procedure reveal an exceptionally tunable strategy\nfor the construction of inert carbon spacers, opening new opportunities\nin synthesis.