Carbon Monoxide Surrogate Reagents [C-C Bond Formation]

　Manabe et al. have investigated novel CO surrogate agents focused on formic acid derivatives and found that 2,4,6-trichlorophenyl formate (T3121) can act functionally as a CO equivalent.¹⁾ This compound is a stable crystalline solid at room temperature and it rapidly decomposes into CO and 2,4,6-trichlorophenol by treatment with a trialkylamine. In situ generated CO is successfully applied to the palladium-catalyzed carbonylation of aryl/alkenyl halides and triflates to give their 2,4,6-trichlorophenol esters. Continuously, the given esters can be transformed into the corresponding carboxylic acid derivatives by the reaction with various nucleophiles. This carbonylation reaction is a highly practical synthetic method since it does not decrease the reaction yields even in gram-scale reactions.²⁾

　Subsequently, Manabe et al. have developed the reductive carbonylation using N-formylsaccharin (F0854) as a CO equivalent.³⁾ In this reaction, palladium acetate is used as a catalyst and the reaductive carbonylation of aryl bromides is accomplished in combination with triethylsilane as a nucleophile. The hydrogen atom on a formyl group of formed aldehydes is introduced by the addition of the hydride species from triethylsilane.