Thiocarbonyl Compounds in [4+2] Cycloadditions: Preparative Aspects

[4+2] Cycloadditions of thiobenzophenones 1a and thiofluorenones 2 with cyclic and open-chain dienes gave cycloadducts in high yields. Assignment of the product structure especially the regiochemistry of the cycloadditions involved 1H- and 13C-NMR spectroscopy, and single-crystal structure determination.