Regiospecificity in the diels‐alder reaction of 1,2,4‐trichloro‐3,5,5‐trimethoxycyclopentadiene.

Some Diels‐Alder adducts of 1,2,4‐trichloro‐3,5,5‐trimethoxycyclopentadiene were prepared and their structure elaborated by chemical transformations. By this it was established that a preferred formation of the 5‐endo‐substituted adducts is found for allyl bromide and allyl acetate, while acrolein yields an excess of the 6‐endo‐isomer.