Carbopalladation of Maleate and Fumarate Esters and 1,1-Dimethylallene with Ortho-Substituted Aryl Palladium Complexes

Abstract

Dimethyl maleate and dimethyl and diethyl fumarates (RO2CCH═CHCO2R) have been reacted with [Pd(C6H4Ro-2)Y(N∧N)] (Ro = OH, CHO, CN, Y = Br, I, N∧N = tmeda, bpy, dtbbpy; 1:1:4.5 molar ratio) and TlOTf to afford complexes resulting from the stereoselective insertion of the olefin and coordnation to Pd of one carbonyl oxygen, giving an enantiomeric mixture of the five-membered metallacyclic complexes [Pd{κ2C,O-2-[CH(CO2R)CHCO2R]C6H4Ro}(N∧N)]OTf (R = Me, Et). From dimethyl maleate, the isolated complexes were RR/SS mixtures with Ro = OH, N∧N = tmeda (2aOH), dtbbpy (2cOH) and N∧N = bpy, Ro = CHO (2bCHO), CN (2bCN) and from the fumarates RS/SR mixtures with N∧N = bpy, Ro = CHO, R = Me (3bCHO), Et (4bCHO). Complex 2bCHO reacts with RNC in a 1:1 or 1:3 molar ratio to give the complexes [Pd{2-[CH(CO2R)CHCO2R]C6H4CHO}}(CNR′)n(bpy)3−n]OTf (R = Me, n = 1, R′ = Xy (5bCHO), tBu = (6bCHO); n = 3, R = Xy (7bCHO), tBu = (8bCHO)). Similarly, the fumarate derivative 3bCHO or 4bCHO afforded the corresponding complexes where R = Me, n = 1, R′ = Xy (9bCHO), n = 3, R′ = tBu (10bCHO) or R = Et, n = 3, R′ = Xy (11bCHO), tBu (12bCHO), respectively. 1,1-Dimethylallene reacts with [Pd(C6H4OH-2)I(N∧N)] to give the η3-allyl complexes [Pd{η3-CH2C(C6H4OH-2)CMe2}(N∧N)]OTf (N∧N = tmeda (13aOH), dtbbpy (13cOH)). The crystal structures of 2aOH, 4bCHO, 7bCHO, and 13aOH have been determined.