Palladium-Catalyzed Cyclization-Heck Reaction of Allenamides: An Approach to 3-Methylene-5-phenyl-1,2,3,4-tetrahydropyridine Derivatives

Abstract

An efficient one-pot construction of functionalized 3-methylene-5-phenyl-1,2,3,4-tetrahydropyridine derivatives via palladium-catalyzed cyclization-Heck reaction of allenamides has been described. The 3-methylene-5-phenyl-1,2,3,4-tetrahydropyridine derivatives feature a nonconjugated diene, including one endo-enamine and one exocyclic double bond, which could be used for further transformation. Both aryl and vinyl halides performed very well under the standard conditions, delivering the corresponding products efficiently.

Pd/PC‐Phos‐Catalyzed Enantioselective Intermolecular Denitrogenative Cyclization of Benzotriazoles with Allenes and N‐Allenamides

“…To elucidate the proposed mechanism, several control reactions were conducted by addition of either external nucleophiles or by using 1,3‐disubstituted allenes with or without a nucleophile, but no other types of products were detected (see the Supporting Information). Based on the above results and some relevant precedents, we propose a plausible mechanism to account for this palladium‐catalyzed denitrogenative cyclization reaction (Scheme ). Benzotriazoles ( 1 ) undergo a ring‐chain isomerization to form the corresponding diazonium l‐A by a Dimroth‐type equilibrium .…”

Recent Development in Palladium-Catalyzed Domino Reactions: Access to Materials and Biologically Important Carbo- and Heterocycles

“…Two new C-C bonds were formed in one pot, mediated by a Pd-π-allyl intermediate in the presence of Pd(PPh3)4 (10 mol%), Cy2NMe (2.0 equiv), in dioxane for 8 h Scheme 33). 54 Scheme 33. Synthesis of 3-methylene-5-phenyl-1,2,3,4-tetrahydropyridine derivatives.…”

π-Allylpalladium Complexes in Synthesis: An Update

“…Liu and co-workers reported the synthesis of functionalized 5-phenyl-1,2,3,4-tetrahydropyridines by the cyclization-Heck reaction of allenamides 177 with both aryl and vinyl halides 178. 72 Since the starting allenamides bear a double bond, the nitrogen derivatives contained both an endo-enamine and one exocyclic double bond, useful for eventual further transformations. The reaction selectively afforded the C 1 product 179/180 and no C3 cyclization product was detected; more than 29 examples were reported (Scheme 52).…”