The synthesis and stereospecific solid-state photodecarbonylation of hexasubstituted meso- and d,l-ketones.

Tertiary carbanions were trapped with half an equivalent of diphosgene to give meso- and d,l-hexasubstituted ketones in moderate yields and modest diastereoselectivities. The ketones were also synthesized by a step-wise synthesis in which the carbonyl group was first installed as an acid before activation and the second nucleophilic attack. This second method gave lower yields but similar diastereoselectivites. Steric limits of both methods were also determined. The photolysis of the resulting crystalline ketones gave a mixture of products in solution, but took place chemoselectively and diastereospecifically in the solid-state.