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

Article abstract of DOI:10.1246/bcsj.68.1437

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 photoreaction of 15c did not give the corresponding styrene, but afforded several products containing 2,4,6-tri-t-butylbenzothiophene 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.