The first examples of cycloadditions of 2-diazo-1,3-dicarbonyl compounds to aromatic thioketones

Acyclic 2-diazo-1,3-dicarbonyl compounds react at 20-50 degrees C with aromatic thioketones and through a cascade process, involving the cycloaddition of a diazo group dipole with the C=S bond, elimination of nitrogen from the arising thiadiazoline, and subsequent [1,5]-electrocyclization of the intermediate C=S-ylide, the relevant oxathioles being formed in yields of up to 70%. Carbocyclic 2-diazo-1,3-diketones at room temperature react with thiones much more slowly, but with increasing temperature they partly decompose to produce, via Wolff rearrangement, 2-oxoketenes, which yield [4+2]-cycloaddition products, that is oxathiinones and/or oxoketene dimers. (C) 2012 Elsevier Ltd. All rights reserved.