Ring-opening Reaction of 6,8-Di-t-butyl-1,2,3,4-tetrahydro-9aH-pyrido [2,1-b] benzoxazole

Treatment of 6, 8-di-t-butyl-1, 2, 3, 4-tetrahydro-9aH-pyrido [2, 1-b]benzoxazole (3a) with conc, hydrochloric acid gave 2,4-di-t-butyl-6-piperidino-phenol (4) and 2,4-di-t-butyl-6-(2-oxopiperidino)phenol (5) in 26 and 25% yields. Reaction of 3a with acetic anhydride afforded 2,4-di-t-butyl-6-[1-(1, 2, 3, 4-tetrahydro-5-acetylpyridyl)] phenyl acetate (6) and 6, 8-di-t-butyl-1-acetyl-2, 3, 4, 4a-tetrahydropyrido [2, 1-b] benzoxazole (7) in 41 and 25% yields. Hofmann degradation of the quarternary salts of 3a with methyl and ethyl iodide gave the expected ring-opend [1, 4] oxazonines, 10a and 10b, in 43 and 10% yields, respectively.