Observation of the Direct Products of Migratory Insertion in Aryl Palladium Carbene Complexes and Their Subsequent Hydrolysis

Abstract

The interaction of an electrophilic carbene carbon atom with the π‐electron density of an aryl group favors an intramolecular migratory insertion reaction (see scheme; Pf=C6F5). This reaction gives alkyl compounds (2 or 3) which can be identified prior to their eventual hydrolysis to 4.

Palladium-Catalyzed Hydroarylation of Diazoacetic Ester

“…Then addition of diazocompound to this complex could generate carbene complex B. 15 The migration of the aryl group to the carbene center, which is now presented in several publications, 16,17 would produce benzylic intermediate C.…”

Palladium-Catalyzed Hydroarylation of Diazocarboxylates and Diazophosphonates

“…Then addition of diazo compound to this complex could generate carbene complex B. 12 Migration of the aryl group to the carbene center, which is now described in several publications, 13,14 would produce benzylic intermediate C. The exchange complex D can be easily produced by substitution of halogen with formate anion followed by liberation of carbon dioxide (complex E). Reductive elimination should provide the product simultaneously with regeneration of the Pd(0) species.…”

Reactive Palladium Carbenes: Migratory Insertion and Other Carbene–Hydrocarbyl Coupling Reactions on Well‐Defined Systems

“…Thus, the putative palladium methoxycarbenes in Scheme must undergo a fast migratory insertion reaction even when the hydrocarbyl group on palladium is pentafluorophenyl, a fragment that forms a strong Pd–C bond and it is known to undergo slower insertion reactions that a phenyl group . With a right choice of substituent R 1 on the carbene fragment, the resulting palladium alkyls ( C , Scheme ) can be trapped by formation of a palladium allyl ( 36 ),, or a palladium benzylic complex ( 37 ) , . For R 1 = Me a fast β‐H elimination leads to the arylated vinyl ether (Scheme ).…”

“…The reaction of the monoamino carbene tungsten complex with the pentafluorophenyl palladium precursor led to the formation of a dimeric palladium carbene ( 38 ) that can be isolated and used as starting material for the synthesis of other [Pd(C 6 F 5 )(carbene)LX] derivatives (Scheme ) . In contrast to the methoxy carbene, the better electron‐donor amino group reduces the electrophilicity of the palladium carbene fragment and increases the stability of the complexes.…”