Heck Couplings with In Situ Generated Diazonium Salts
ArNH2 + CH2=CHCO2Me → ArCH=CHCO2Me
The Heck-Matsuda coupling involves the generation of a diazonium salt which is then coupled with an olefin. In this paper, the reaction is run with a sub-stoichiometric amount of methanesulphonic acid (10-20mol%) in methanol which limits the amount of diazonium salt that can be present at any one time during the reaction. tert-Butyl nitrite is used for the diazotisation and palladium acetate is used as the catalyst or the Heck coiupling. In addition the reaction is amenable to use in an HRC (Heck-Reduction-Cyclisation) cascade process where 4-methoxy-2-nitroaniline and methyl acrylate are converted in to 7-methoxy-3,4-dihydro-1H-quinolin-2-one in 80% yield. 12 examples, yields 51-99% (74-99% for 11 of the 12 examples).
F. Le Callonnec, E. Fouquet, and F.-X. Felpin, Org. Lett., 2011, 13, 2646-2649.