(2endo)-2-Chloro-4,4-dimethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (2) and (2endo)-2-chloro-1,4,4-trimethyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (3) via [4+3] cycloaddition of an oxyallyl intermediate generated from 1,3-dichloro-3-methylbutan-2-one in 2,2,2-trifluoroethanol
Molbank