Preparation and Reactivity of 1,3-Bis(alkylthio)allenes and Tetrathiacyclic Bisallenes

Reactions of Ph₂C₃ dianion, prepared from 1,3-diphenylpropyne and n-butyllithium, with alkyl thiocyanates or alkane dithiocyanates gave 1,3-bis(alkylthio)allenes 1 or tetrathiacyclic bisallenes 2, respectively. Thermal reactions of 1 gave thiophenes 4 and 7, benzothiepin 5, 1,2-bis(benzylidene)cyclobutane 6, thiete 8, and α,β-unsaturated ketone 9, and the reactions of tetrathiacyclic bisallenes 2a gave a cyclic dimer, 1,2-bis(benzylidene)cyclobutane derivative 10, quantitatively. Irradiation of 1,3-bis(alkylthio)allenes 1 and tetrathiacyclic bisallenes 2a caused rearrangement to give alkynes 18, 20, and 21. In the irradiation of the cyclic bisallenes 2a, isomerizations from dl to meso and meso to dl isomers were also found. In the reactions of allenes 1 and cyclic bisallenes 2a with diphenyl diazomethane, the diazomethane reacted selectively with the double bond rather than with the sulfur atom.