A Novel Approach to Synthesis of 1R-Cis-Caronaldehyde a key Intermediate for Photostable Pyrethroid Insecticides

Abstract

The bicyclic hydroxy γ-lactone, cis-(-)-4 α-hydroxy-6, 6-dimethyl-3-oxa-bicyclo (3, 1, 0)-hexan-2-one (1), commonly known a s 1R-cis-caronaldehyde, is an important intermediate for the highly potent pyrethroids Deltamethrin (2) and NRDC 182 (2). The latter is the biologically active isomer in commercial cypermethrin. In our laboratory we have obtained excellent yields of (1) by the reductive ozonolysis2 of the enol lactone 4 obtained by the cyclization of the keto acid (2) which in turn is derived from the abundantly available (+)-3-carene.