Palladium-Catalyzed Carbene Insertion and Trapping with Carbon Nucleophiles
摘要:
Palladium catalysts are shown to catalyze the three-component coupling of vinyl halides, trimethylsilyldiazomethane, and stabilized carbon nucleophiles. The reaction is believed to proceed through a palladium-carbene intermediate LX(R)Pd=CHSiMe3 that undergoes migration of the vinyl substituent to the electrophilic carbene center to generate an eta(3)-allylpalladium intermediate. The allylpalladium intermediate is attacked by the carbon nucleophile to generate a vinylsilane product.
rare 1,1-dipole synthons, allyl sulfones are rarely used in target-oriented syntheses, likely due to the lack of a general catalytic method for their branch-selective allylicsubstitution. Herein, we identified allyl 4-chlorophenyl sulfone as a versatile linchpin for both base-mediated α-derivatization and subsequent cobalt-catalyzed allylicsubstitution. The sequential transformations allow for highly
A cobalt(I)-catalyzed regioselective allylic alkylation of tertiary allylic carbonates with 1,3-dicarbonyl compounds is described. The alkylated products are obtained in high yields and with excellent selectivity towards the kinetic branched regioisomer. Mechanistic insights by combining experimental and computational investigations support a Co(I)/Co(III) catalytic cycle.