Reactions of (2,4,6-Tri-t-butyl)thiobenzaldehyde with Diazo Compounds. Synthesis and Reactions of Sterically Congested Thiiranes

Abstract

Abstract Sterically congested thiiranes having a 2,4,6-tri-t-butylphenyl group were synthesized by the reactions of (2,4,6-tri-t-butyl)thiobenzaldehyde with sterically hindered diazo compounds. Thermal desulfurization of the most congested thiirane, 2,2-di-t-butyl-3-(2,4,6-tri-t-butylphenyl)thiirane (15c), did not proceed even upon using highly reactive reagents, such as hexamethylphosphorous triamide or organolithiums. The photo-reaction of 15c did not give the corresponding styrene, but afforded several products containing 2,4,6-tri-t-butylbenzo[b]thiophene and Dewar benzenes, 2,2-di-t-butyl-3-(3,4,6-tri-t-butylbicyclo[2.2.0]hexa-2,5-dien-2-yl)thiirane and 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene (24), the latter of which is the first example for a vinyl-substituted Dewar benzene. Compound 24 has a unique reactivity, giving a rearrangement product, 2-t-butyl-3,3-dimethyl-1-(1,3,5-tri-t-butylbicyclo[2.2.0]hexa-2,5-diene-2-yl)-1-butene on thermolysis.