Reactivity and Selectivity of Ortho-Metalated Rhodium(II) Complexes in C−H Insertion Reactions of α-Diazo Compounds

Regioselective intramolecular C−H insertion reactions of α-diazo β-keto esters and α-diazo ketones are mediated by Rh 2 [OOCR] 4 - x [PC] x ( x = 1, 2; PC = ortho-metalated phosphine; R = CH 3, C 3 F 7 ). In particular, the intramolecular transformation of 1-diazo-5-methyl-3-propyl-2-hexanone catalyzed by Rh 2 [OOCCH 3 ] 2 [PC] 2 (PC = (C 6 H 4 )P(C 6 H 5 ) 2, head-to-tail (H−T) configuration) afforded only the tertiary C−H insertion product. By comparison, no C−H insertion reaction was promoted by doubly metalated complexes with a head-to-head (H−H) configuration. Rh 2 [OOCR] 3 [PC] compounds were found to be less suited for these type of reactions.