A diverse sample of thiocarbonyl compounds were examined to determine what the ultimate stable products are of their reactions with dimethoxycarbene. Those ultimate products can be significantly different for an oxyphosphinyl dithioformate, methyl dithiobenzoate, O-methyl thiobenzoate, and dimethyl xanthate. Key words: dimethoxycarbene, thiocarbonyl compounds, 2,5-dihydro-2,2-dimethoxy-5,5-dimethyl-1,3,4-oxadiazole.