Reductive Coupling of Aldehydes by H2S in Aqueous Solutions, a CC Bond Forming Reaction of Prebiotic Interest

Abstract We report here a novel reductive coupling reaction of conjugated, non‐ or poorly enolizable aldehydes induced by H 2 S and operative in aqueous solutions under prebiotically relevant conditions. This reaction leads from retinal to β ‐carotene, and from benzylic aldehydes to the corresponding diarylethylenes. This novel reaction also opens a new potentially prebiotic pathway leading from glyoxylic acid to various compounds that are involved in the reductive tricarboxylic acid cycle. This CC bond forming reaction of prebiotic interest might have been operative, notably, in the sulfide‐rich environments of hydrothermal vents, which have been postulated as possible sites for the first steps of organic chemical evolution.