87682-65-3Relevant academic research and scientific papers
Synthesis of 3,3-Dichloropiperidines and Further Functionalization via Pd-Catalyzed Cross-Coupling Reactions of the Dichloromethylene Moiety
Van Beek, Wim E.,Smets, Robert J.,Kushwaha, Khushbu,Herrebout, Wouter A.,Abbaspour Tehrani, Kourosch
, p. 95 - 103 (2019)
A new synthetic methodology for the functionalization of the dichloromethylene moiety in 3,3-dichloropiperidines via Pd-catalyzed cross-coupling reactions is reported. A range of 3,3-dichloropiperidines was synthesized via a hydride induced cyclization of α,α,δ-trichloroaldimines or an indium(III) triflate catalyzed alkynylation/cyclization procedure of α,α,δ-trichloroaldimines. Subsequently, a dehydrochlorination followed by a cross-coupling with the thus formed vinylic chloride was envisioned. The non-alkynylated 3,3-dichloropiperidines could be regioselectively eliminated and by careful choice of solvent and base both of the two regioisomeric vinyl chlorides could be exclusively formed. Palladium-catalyzed Suzuki cross-coupling of the thus formed 5-chloro-1,2,3,6-tetrahydropyridines led to C3-substituted 1,2,3,6-tetrahydropyridines, which could be easily reduced to 3-substituted piperidines, generating therapeutic agent (±)-Preclamol for example. The 2-alkynyl-3,3-dichloropiperidines were regioselectively eliminated giving the cyclic enamine, which was subsequently cross-coupled in one-pot. The presence of the alkynyl function, in this case, clearly directs elimination towards enamine structures. Hydrogenation of the resulting, unstable 2-alkynyl-3-substituted-1,2,3,4-tetrahydropyridines, yields stable 2,3-disubstituted piperidines.
