Studies of some pinane monoterpenes (1964)
AuthorsWallis, A. F. A.show all
Bromination of isopinocamphone gave 2α, 4α-dibromo-10β-pinan-3-one which on treatment with boiling aqueous acetic acid or N,N-dimethylformaide gave 3-endo, 6-endo-dibromocamphor, the second "product"of the bromination reaction. Enol acetylation of isopinocamphone by acetic anhydride – perchloric acid or isopropenyl acetate –ϝ-toluene suphonic acid gave the Δ²-enol acetate which on bromination yielded 2α-bromo-10β-pinan-3-one. Under hydrogen bromide conditions, the 2α-mono-bromoketone was isomerised to a mixture containing the 4-mono-bromoketone. Bromine addition to pinocarvone afforded 2α,10-dibromo-10β-pinan-3-one, which on hydrogen bromide treatment gave α,10-dibromo-10β-pinan-3-one. The reaction of hydroge bromide on pinocarvone gave a mixture of epimeric 10-bromopinan-3-ones. Dehydroromination of the α,10-dibromoketone yielded α-bromopinocarvone. Reaction of bromine on the 2α,10- and 4α,10-dibromoketones and 4α-bromopinocarvone afforded 2α, 4α, 10-tribromo-10α-pinan-3-one, which rearranged to 3-endo, 6-endo, 10-tribromocamphor on treatment with boiling aqueous acetic acid. The addition of hydrogen bromide to trans-pinocarveol gave 6-endo-bromo-exo-isofenchol, which gave 6-endo-bromoisofenchone on oxidation, and 2,2,4-trimethyl-cyclopent-3-ene-1-acetaldehyde with silver acetate-acetic acid. Sodium borohydride reduction of the bromoisofenchone afforded 6-endo-bromo-endo-isofenchol. Addition of hydrogen bromide to cis-pinocarveol yielded 6-endo-bromoisoborneol, which was oxidised to 6-endo-bromocamphor, and dehydrobrominated to campholenic aldehyde. A preliminary study has been made of the addition reactions of both myrtenal and myrtenol. Trans-Verbenol, 10β-pin-3-en-2α-ol and their acetates have been shown to give similar products to vervene on treatment with hydrogen bromide. Addition of hydrogen bromide to vervenone gave a rearranged bromoketone mixture. α-Pinene oxide reacted with boron trifluroide to give seven products, six of which have been identified as rearranged materials. Several other requirement reactions of α-pinene oxide have been studied.