Diazo compounds thiocarbonyl ylides

Heimgartner and co-workers treated a-diazoketones and a-diazoamides 64 with thiones, with and without a catalyst such as Rh(OAc)2 present (1998HCA285). The products were substituted thiiranes 65 and/or substituted 1,3-oxathioles. In all cases, a thiocarbonyl ylide intermediate, which could undergo either a 1,3- or a 1,5-electro-cyclization, was held responsible. The ylide could arise either from addition of a carbene or a carbenoid to S of the thiocarbonyl compound or by loss of N2 from a primary cycloadduct between the diazo and the thiocarbonyl compounds. In one case, such a primary adduct was isolated. The thiirane carboxamides could be desulfurized with (Me2N)3P in tetrahydrofuran (THF) at 60 °C to afford acrylamides 66 (Scheme 11). 

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