Dehydroannulenes. X. Synthesis and Properties of 3,9,12,18-Tetra-substituted-1,10-bisdehydro[18]annulenes

The cyclic dimerization of 1,7-disubstituted-1-oxo-2,4,6-nonatrien-8-ynes on treatment with a suspension of potassium hydroxide in liquid ammonia to give tetrasubstituted 18-membered cyclic glycols has been achieved. The cyclic glycols could be converted into 3,9,12,18-tetrasubstituted 1,10-bisdehydro[18]annulenes which were found to be conformationally stable and strongly diatropic.