Carbenoid Reactions in Rhodium(II)‐Catalyzed Decomposition of Iodonium Ylides

Abstract

Abstract The intermediacy of metallocarbenes in decomposition reactions of iodonium ylides with [Rh 2 (OAc) 4 ] was established by comparison with reactions of the corresponding diazo compounds. The sensitivity of the Rh II ‐catalyzed intermolecular cyclopropane formation from substituted styrenes and bis(methoxycarbonyl)(phenyliodono)methanide ( 1a ) or dimethyl diazomalonate ( 1b ) is identical. The Hammett plot (with σ + ) has a slope of −0.47. Iodonium ylides and diazo compounds afford the same products in [Rh 2 (OAc) 4 ]‐catalyzed cyclopropane formations, cycloadditions, and intramolecular CH insertions, and exhibit the identical selectivity in intramolecular competitions for cyclopropane formation and insertion. The intramolecular CH insertion of the ylide 20c , when carried out in the presence of a chiral catalyst ([Rh 2 {(−)‐( S )‐ptpa} 4 ]), results in formation of 21a having an ee of 67%, identical to the ee obtained with the diazo compound 20b .