Thermal cycloaddition reactions of thiocarbonyl compounds. Part 1. A novel [4 + 2] cycloaddition reaction of adamantanethione with α,β-unsaturated carbonyl compounds

Abstract

The thermal cycloaddition reaction of adamantanethione (1) with α,β-unsaturated carbonyl compounds such as acrolein, methacrolein, and methyl vinyl ketone occurred smoothly at 80–140 °C to afford, regioselectively, adamantane-2-spiro-2′-(1′-oxa-3′-thiacyclohex-5′-enes)(3a–e) as novel [4 + 2] cycloadducts in good yield. The nature of this cycloaddition is discussed on the basis of kinetics, solvent effects, and FMO theory.