Preparation of cyclic aromatic carbonates

摘要

Cyclic carbonates of the formula wherein A and B are aromatic radicals, R is attached to A and B ortho relative to the oxygen atoms and is an alkylidene radical, and n is 0 or 1, are obtained by heating under a reduced pressure a carbonate polymer of the formula Suitable polycarbonates are those in which A and B are phenyl, diphenyl or naphthyl groups, optionally substituted by alkyl, aralkyl, alkoxy, sulphone and nitro radicals or halogen atoms. Reaction temperatures are generally in the range 250-350 DEG C. or higher, but lower temperatures may be employed if a depolymerization catalyst is used. A vacuum of the order of 50 mm. is suitable. Examples relate to the preparation of 2,21-(diphenyl)-carbonate, 2,21-(diphenylmethane)-carbonate and 2,21-(5,51-dimethyldiphenylmethane)-carbonate.