Thermal decomposition of 4-(4-hydroxyphenyl)-2,2,4-trimethylchromane (
1) gives 2,2,4-trimethyl-2H-chromen (2) and 2,2-dimethyl-4-methylenech
roman (3). Under influence of hydrochloric acid, 3 isomerizes smoothly
to 2. Under similar reaction conditions 2'-hydroxy-2,4,4-trimethylfla
van (4) is transformed into 2 and 2,4,4-trimethyl-4H-chromen (5); elim
ination of the phenol moiety is accompanied with a rearrangement. open
ing of the pyran ring with subsequent re-cyclization seems to be more
reliable explanation of this transformation than simple 1-3 migration
of the methyl group.