In this work I investigated precursor systems for mercaptocarbenes, a species little is known about to date. We reported the generation of hydroxymercaptomethylene (HO–C̈–SH) that is remarkably stable under cryogenic conditions at 3 K and that does not show any tunneling reactions. We also reported the photochemical generation of aminomercaptomethylene (H2N–C̈–SH) in its complex with CO2 from 2-amino-2-thioxoacetic acid. This complex undergoes backreaction to the starting material by heavy atom tunneling. On the search for a suitable precursor system for phenylmercaptomethylene (Ph–C̈–SH) we noticed the formation of a thiophene derivative. This simple one-pot reaction starting from substituted α-keto carboxylic acid esters to substituted thiophenes represents a new synthetic approach towards these substituted heterocycles.
