On the most powerful chemical traps for bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene)

The efficiency and validity of different chemical substrates for trapping bis(methoxycarbonyl)carbene ( 2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene; 1) is dependent on the conditions of carbene generation. On conventional photolysis of dimethyldiazomalonate (=2-diazopropanedioic acid dimethyl ester; 2) by long-wave UV light (through a Pyrex filter, lambda > 290 nm), the most powerful trap for carbene 1 in the series of substrates Me2S, MeOH, cyclohexane, and pyridine is Me2S (with an efficiency ratio of ca. 6:4:2:1, resp.). When short-wave decomposition of diazomalonate 2 is employed (through a quartz filter, A > 210 nm), more reliable and useful chemical traps for bis(methoxycarbonyl)carbene (1) are pyridine and cyclohexane, whose adducts with 1 are rather stable under short-wave-irradiation conditions. Application of alcohols for the trapping of I proves to be preferential when simultaneous monitoring of carbene and oxoketene formation during photolysis is necessary.