Thiocarbonyl ylides : Reactions and stereochemical properties of some 4-t-butylcyclohexyl derivatives

The azine from 4-t-butylcyclohexanone on treatment with hydrogen sulfide under pressure is converted to a mixture of stereoisomeric 1,3,4-thiadiazolidines. Dehydrogenation of this mixture with an alkyl azodicarboxylate afforded in quantitative yield (based on azine) a mixture of the three possible Δ³-1,3,4-thiadiazolines. These three isomers have been isolated and their structures have been established as trans,trans-3,11-di-1,1-dimethylethyl]-14,15-diaza-7-thiadispiro5.1.5.2]pentadeca-14-ene(5); the cis,cis-isomer (6), and the cis,trans-isomer (7). Pyrolysis of either 5 or 6 leads in quantitative yield to cis,trans-3,10-di-1,1-dimethylethyl]thiadispiro5.0.5.2]tridecane (8), the formation of which is rationalized by conrotatory ring closure of the same thiocarbonyl ylide (24) formed from either 5 or 6. Pyrolysis of 7 leads exclusively to a thiirane isomeric with 10 and which is assigned the cis,cis-structure (9). The thiiranes 8 and 9 are desulfurized by tri-n-butylphosphine to the anti- and syn-1-(1,1-dimethylethyl)-4-4-(1,1-dimethylethyl)cyclohexylidene]cyclohexanes (11 and 12), respectively. The cycloadditions of the thiocarbonyl ylides derived from 5–7 with dimethyl acetylenedicarboxylate and dimethylazodicarboxylate have been examined but stereochemistries have not been assigned to these products. Cis additions to the olefins (11 and 12) have been investigated with the most attention having been paid to the reactions with osmium tetroxide. The configurations of the glycols expected from these reactions have been correlated by comparison with the three possible glycols (16–18) obtained from pinacol reduction of 4-t-butylcyclohexanone. These three glycols have been separated and their configurations assigned from PMR and IR data. A discussion of the stereochemical implications of the various results is given.