Substituent effects on the cyclization mode of 7-sulfonyl-3-hepten-1,5-diynes and 11-sulfonylundeca-3,7-dien-1,5,9-triynes

In probing of cycloaromatization of 7-phenylsulfonyl-3-hepten-1,5-diyne systems to generate biradical intermediates under an alkaline condition suggested that the aryl moiety on C3–C4 also plays an important role to switch the Myers cyclization to Schmittel cyclization in the allen–enyne system, although the aryl group on the alkyne terminus does not work in the proceeding of the cycloaromatization. For example, treatment of 1-phenyl-7-phenylsulfonyl-3-hepten-1,5-diyne () with triethylamine in the presence of 1,4-cyclohexadiene in benzene offered biphenyl in 51% yield. Under the same reaction conditions, cyclization of 1-(2-phenylethynyl)-2-(3-phenylsulfonyl-1-propynyl) benzene () gave naphthalene in 42% yield along with indene in 32% yield. Moreover, the substituent effect also occurred in the cyclization of 11-phenylsulfonylundeca-3,7-diene-1,5,9-triyne (), which provided indene in 50% yield as the major product.