Van Beek, Wim E. published the artcileSynthesis of 3,3-Dichloropiperidines and Further Functionalization via Pd-Catalyzed Cross-Coupling Reactions of the Dichloromethylene Moiety, COA of Formula: C5H6BNO2, the publication is European Journal of Organic Chemistry (2019), 2019(1), 95-103, database is CAplus.
A new synthetic methodol. 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.
European Journal of Organic Chemistry published new progress about 197958-29-5. 197958-29-5 belongs to pyridine-derivatives, auxiliary class Pyridine,Boronic acid and ester, name is 2-Pyridinylboronic acid, and the molecular formula is C8H6ClF3, COA of Formula: C5H6BNO2.
Referemce:
https://en.wikipedia.org/wiki/Pyridine,
Pyridine | C5H5N – PubChem