Alkylthio(4-methylpent-3-en-1-ynyl)carbenes: generation by the photolysis of 5-alkylthioethynyl-3,3-dimethyl-3H-pyrazoles and reactions with alkenes

New singlet alkylthio(4-methylpent-3-en-1-ynyl)carbenes were generated by photolysis of corresponding 5-alkylthioethynyl-3,3-dimethyl-3H-pyrazoles and subsequently trapped by alkenes giving rise to 1-alkynyl-1-(alkylthio)cyclopropanes in yields up to 60%.