The simple refluxing of allenynes, having a phenylsulfonyl functionality on the allenyl group, in xylene (or mesitylene) without microwave irradiation resulted in the efficient formation of bicyclo [5.2. 0] nona-1, 7-dienes and bicyclo [4.2. 0] octa-1, 6-dienes in high yields. This method was shown to be successfully applicable to the first construction of bicyclo [6.2. 0] deca-1, 8-dienes. Construction of the corresponding oxa-and azabicyclo [m. 2.0] ...