Catalytic Hunsdiecker reaction of α,β-unsaturated carboxylic acids: How efficient is the catalyst?

Article abstract of DOI:10.1021/jo025868h

UV-vis spectrophotometry is utilized to measure the relative efficiency of lithium acetate, tetrabutylammonium trifluoroacetate, and triethylamine as catalysts for the conversion of 4-methoxycinnamic acid to 4-methoxy-β-bromostyrene. In acetonitrile - water as solvent, the efficiency order is lithium acetate > triethylamine > tetrabutylammonium trifluoroacetate. For triethylamine as catalyst, solvent-dependent order is acetonitrile - water > dichloromethane > acetonitrile. Using triethylamine as catalyst (5-20 mol %), cinnamic acids, and propiolic acids are converted to corresponding β-bromostyrenes and 1-halo-1-alkynes in 60-98% isolated yields within 1-5 min.