Unusual Ring Opening of Bicyclic Terpenes during Pd‐catalyzed Coupling with Aromatic Halides

Abstract Herein we describe Pd‐catalyzed cross‐coupling reaction of α ‐pinene derivative – pinacarvone O ‐methyl oxime ( 1 ) with aryl halides ( 2 ). Surprisingly, the formation of the C−C coupling product was accompanied by an unexpected opening of the pinene bicyclic structure. The ( Z )‐2‐aryl‐4,4,5‐trimethylcyclohexa‐2,5‐dien‐1‐one O ‐methyl oxime ( 3 ) was formed as the resulting product. The reaction conditions of the developed synthetic procedure were carefully optimized and the reaction mechanism was supposed on the basis of data obtained by structural and computational methods.