Propellanes. LXVI. Exo‐ and Endo‐Diels‐Alder adducts of 4‐substituted 1,2,4‐triazoline‐3, 5‐diones with various 1, 6‐methano [10]annulenes

Abstract
Relatively few exo‐adducts have been obtained from the title compounds. Only one such mono‐adduct, 3, is known. Several exo‐endo‐bis‐adducts have been obtained but the structure of one of these, 5, has been proved unequivocally by X‐ray structural determination.