Formation of Cyanohydrin Carbonates of Aromatic Aldehydes and Aryl Heteroaryl Ketones

Abstract

Cyanohydrin derivatives cannot be made by direct addition to diaryl ketones due to the unfavourable equilibrium for the addition process.¹ We required a route to cyanohydrin carbonates of type (1, R¹=heteroaryl, R²=a1kyl), and approached their formation via the aromatic aldehyde analogues (2). Such derivatives (2) have been made using a single aqueous phase method,² and acyl analogues have been made using also a two-phase (water/ether) procedure.³ To obtain the carbonates (2) we have found the former method unreliable and that a satisfactory procedure is to stir an aqueous solution of KCN with the aldehyde and alkyl chloroformate in methylene chloride at 10°C (Table 1). Where necessary yields can be increased by the inclusion of a phase transfer catalyst,⁴ benzyltrimethylammonium chloride. A similar procedure, for addition to (heterocyclic) c=N, has recently been reported⁵ for the formation of certain Reissert compounds.