Recent advances in the synthesis of piperidones and piperidines

Organocatalyzed highly atom economic one pot synthesis of tetrahydropyridines as antimalarials

A highly atom economic one pot synthesis of tetrahydropyridines was achieved by L-proline/TFA catalysed multicomponent reaction of beta-keto-esters, aromatic aldehydes and anilines. The synthesized compounds were screened against Plasmodium falciparum in vitro and one of them showed antimalarial activity with MIC as low as 0.09 microg/mL.

Cyclic imine nitro-Mannich/lactamization cascades: a direct stereoselective synthesis of multicyclic piperidinone derivatives

An efficient nitro-Mannich/lactamization cascade of gamma-nitro esters with cyclic imines for the preparation of architecturally complex multicyclic piperidinone ring-containing structures has been developed. The reaction is broad in scope and stereoselective and may be coupled to an enantioselective nitroolefin Michael addition reaction as part of a highly enantio- and diastereoselective multicomponent process.

Synthesis of fused piperidinones through a radical-ionic cascade

Azabicyclo[4.3.0]nonanes were assembled, from chiral allylsilanes possessing an oxime moiety, using a stereocontrolled formal [2 + 2 + 2] radical-ionic process. The cascade involves the addition of an alpha-iodoester to the less substituted end of the enoxime which is then followed by a 5-exo-trig cyclization onto the aldoxime function, producing an alkoxyaminyl radical species which finally lactamizes to afford the titled piperidinone. High levels of stereoinduction were observed, demonstrating the ability of a silicon group located at the allylic position to efficiently control the stereochemistry of the two newly created stereogenic centers. When the radical cascade was extended to ketoximes, the resulting sterically hindered alkoxyaminyl radical did not react further with the initiator Et3B to produce the expected nucleophilic amidoborane complex. In sharp contrast, this long-lived radical recombined with the initial alpha-stabilized ester radical to produce a cyclopentane incorporating two ester fragments.

An efficient method for the synthesis of nitropiperidones

A three step efficient strategy for the synthesis of substituted 5-nitropiperidones in high de, employing Michael addition of N-p-tolylsulfinyl beta-nitroamines to alpha,beta-unsaturated esters, hydrolysis of the sulfinyl group, and cyclization of the resulting free amines, has been developed. A very simple experimental procedure involving mild conditions and only one chromatographic purification are the main features of the process.