Studies of heterocyclic compounds. Part 25. Stable indolizine and pyrrolo [2,1-b]thiazole carboselenaldehydes

Abstract

The reaction of indolizines and pyrrolo[2,1-b]thiazoles with phosphoryl chloride in dimethylformamide and treatment of the resulting Vilsmeier salts in situ with aqueous sodium hydrogen selenide gives indolizine and pyrrolo[2,1-b]thiazole carboselenaldehydes, many of which are stable crystalline compounds. ¹H N.m.r. and u.v. spectral data of the selenaldehydes are reported. 2,7-Dimethylindolizine-3-carboselenaldehyde and 5,6-dimethylpyrrolo[2,1-b]thiazole-7-carboselenaldehyde were reduced by lithium aluminium hydride–aluminium chloride to the corresponding trimethyl derivatives. 2,7-Dimethylindolizine-3-carboselenaldehyde and 5,6-dimethylpyrrolo[2,1-b]thiazole-7-carboselenaldehyde smoothly underwent Wittig reactions with isopropylidenetriphenylphosphorane in dimethyl sulphoxide–benzene solution at room temperature, and with acetylmethylenetriphenylphosphorane in boiling xylene.