Cyclodienones. 7. Preparation and Reduction of 1-(3,5-Di-tert-butyl-2-hydroxyphenyl)pyridinium Halides

Article abstract of DOI:10.1021/jo00335a026

The reactions of 4-bromo- (1a) and 4-chloro-2,4,6-tri-tert-butyl-2,5-cyclohexadien-1-one (1b) with compounds such as pyridine (4a), α- (4b), β- (4c), and γ-picoline (4d), and 3,5-lutidine (4e) were carried out under various conditions to produce the corresponding 1-(3,5-di-tert-butyl-2-hydroxyphenyl)pyridinium halides (7) or their intramolecular salts (8).The reduction of 7 and 8 with NaBH4 in methanol afforded in good yields the corresponding tetrahydropyridine derivatives (21), which were reduced to o-piperidinophenols (22) by hydrogenation with Raney Ni (W2) catalyst in high yields.The reaction pathway of the formation of 7 is also discussed.