High pressure-promoted cycloadditions of ketene acetals and α,β-unsaturated aldehydes and ketones

Cycloadditions of ketene acetals with α,β-unsaturated carbonyl compounds are strongly promoted by high pressure. The influence of the solvent and the substitution pattern on the product distribution at 12 kBar has been investigated. In the polar solvent, acetonitrile, α,β-unsaturated aldehydes not having large β-substituents, yield mainly cyclobutane aldehydes, which are minor products at normal pressure. The products can be transformed under basic conditions without ring opening.