Chemistry Letters, Vol.30, No.12, 1284-1285, 2001
Preferential bond activation of sp(3) C-H over sp(2) C-H in alpha,beta-unsaturated carboxylic acids by ruthenium complex
Reactions of Ru(1,5-cod)(1,3,5-cot) (1)/PMe3 [cod = cyclooctadiene, cot = cyclooctatriene] with propenoic acids (CH2=CH(R)COOH) give unsaturated ruthenalactones Ru[OC(O)C(R)=CH-kappa O-2, C](PMe3)(4) [R = Me (2a), Et (2b), Pr (2c), Pr-i (2d)]. In contrast, reactions of trans-2-methyl-2-butenoic acid and 2-methylcinnamic acid (R'CH=C(Me)COOH) give Ru[OC(O)C(CH2R')=CH-kappa O-2, C](PMe3)4 [R'= Me (2b), Ph (2e)] as major products, suggesting the preferential activation of the sp(3) C-H over sp(2) C-H bond on ruthenium(II) center.