The γ-butenolide obtained from an organocatalyzed, direct vinylogous aldol reaction of γ-crotonolactone and benzaldehyde serves as the key starting material in the expedient synthesis of a 3-hydroxy-2-phenyl piperidine intermediate which is converted to the target 2,3-disubstituted piperidines.

Asymmetric hydrogenation is one of the most important enantioselective reactions. Although the hydrogenation, transfer hydrogenation, and hydrosilylation of various substrates in the presence of metal catalysts have been described, the asymmetric reduction of aromatic and heteroaromatic compounds still represents a great challenge. This situation is particularly true for the enantioselective hy...

Trichloroacetic Acid (TCA) was used as an efficient catalyst for the synthesis of highly functionalized piperidines via a one-pot five-component reaction of aromatic amines, aromatic aldehydes and β-keto esters in MeOH at room temperature. The remarkable advantages offered by this method are good yields, simple procedure, short reaction times, no need to column chromatography and an easy wo...

Use of a base-free Pd(DMSO)(2)(TFA)(2) catalyst system enables the synthesis of six-membered nitrogen heterocycles via a Wacker-type aerobic oxidative cyclization of alkenes bearing tethered sulfonamides. Various heterocycles, including morpholines, piperidines, piperazines, and piperazinones, are accessible by this method.

A catalytic enantioselective bromocyclization of olefinic amides using amino-thiocarbamates as the catalysts has been developed. The resulting enantioenriched 2-substituted 3-bromopiperidines can readily be transformed to 3-substituted piperidines through a silver salt-mediated rearrangement. This process has been applied to the synthesis of a dopaminergic drug, Preclamol.

The silyl enol ether derivatives of ketones or esters tethered by a hydrocarbon or ether linkage to the 3-position of a pyridine ring undergo dearomatising nucleophilic attack on the ring once it is activated (as an acylpyridinium species) by the addition of methyl chloroformate. The bicyclic dihydropyridine products are in some cases unstable, but may be isolated after hydrogenation as fused b...

The first chiral phosphine-catalyzed activation of acrylates for intramolecular formal [2 + 4] reactions with unsaturated imines is described. The catalytic reactions afford N-heterocycles with exceptionally high diastereo- and enantioselectivities. The [2 + 4] products are amenable for further transformations to useful molecules such as chiral piperidines and multicyclic structures.

Abstract A method for the synthesis of functionalized piperidines containing 3 contiguous stereocentres in 2-,3- and 4- positions uses a diastereoselective nitro-Mannich to control stereochemistry. The reaction between β-aryl/heteroaryl substituted nitroalkanes glyoxylate imine provides β-nitro-amines with good selectivity (70:30 >95:5) syn, anti-diastereoisomers. Reductive cyclisation BF3.OEt2...