Chemistry Letters, Vol.46, No.7, 1040-1043, 2017
Regioselectivity Control by Added MeCN in Ru(0)-catalyzed Cross-dimerization of Internal Alkynes with Methyl Methacrylate
Ru(eta(6)-naphthalene)(eta(4)-1,5-COD) (1: 10mol%) catalyzes cross-dimerization of internal alkynes 2 with methyl methacrylate (3) to give a regioisomeric mixture of the dienyl ester products, RCH=CRCH=CMeCO2Me (4) and RCH=CRCH2C(=CH2) CO2Me (5) at room temperature. Addition of MeCN (20-100mol%) into this system drastically promotes the formation of 5 by suppressing the formation of 4. The DFT calculations suggest this reaction to proceed by an oxidative coupling mechanism and the coordinated MeCN in the ruthenacycle encourages the regioselective beta-hydride elimination to produce 5.