Carbocyclization of Heterosubstituted Alkynes via the Memory of Chirality: Access to Cα-Substituted Proline Derivatives

Piperidine Derivatives: Recent Advances in Synthesis and Pharmacological Applications

Piperidines are among the most important synthetic fragments for designing drugs and play a significant role in the pharmaceutical industry. Their derivatives are present in more than twenty classes of pharmaceuticals, as well as alkaloids. The current review summarizes recent scientific literature on intra- and intermolecular reactions leading to the formation of various piperidine derivatives: substituted piperidines, spiropiperidines, condensed piperidines, and piperidinones. Moreover, the pharmaceutical applications of synthetic and natural piperidines were covered, as well as the latest scientific advances in the discovery and biological evaluation of potential drugs containing piperidine moiety. This review is designed to help both novice researchers taking their first steps in this field and experienced scientists looking for suitable substrates for the synthesis of biologically active piperidines.

Memory of Chirality in the Asymmetric Synthesis of Piperidines with Vicinal Stereocenters by Intramolecular Sn2' Reaction

Intramolecular Sn2' cyclization of α-amino ester enolates provided piperidine derivatives with vicinal quaternary-tertiary stereocenters with excellent diastereo- and enantioselectivity via memory of chirality and the Thorpe-Ingold effect. DFT calculations provided a mechanistic rationale for the increase in chirality preservation via the Thorpe-Ingold effect. This new method has the potential to be integrated into concise asymmetric synthesis of bioactive molecules containing multisubstituted piperidine moieties.

Chirality memory of α-methylene-π-allyl iridium species

Chirality is one of the most important types of steric information in nature. In addition to central chirality, axial chirality has been catching more and more attention from scientists. However, although much attention has recently been paid to the creation of axial chirality and the chirality transfer of allenes, no study has been disclosed as to the memory of such an axial chirality. The reason is very obvious: the chiral information is stored over three carbon atoms. Here, the first example of the memory of chirality (MOC) of allenes has been recorded, which was realized via an optically active alkylidene-π-allyl iridium intermediate, leading to a highly stereoselective electrophilic allenylation with amines. Specifically, we have established the transition metal-mediated highly stereoselective 2,3-allenylation of amines by using optically active 2,3-allenyl carbonates under the catalysis of a nonchiral iridium(iii) complex. This method is compatible with sterically bulky and small substituents on both amines and 2,3-allenyl carbonates and furnishes the desired optically active products with a high efficiency of chirality transfer. Further mechanistic experiments reveal that the isomerization of the optically active alkylidene-π-allyl iridium intermediate is very slow.

Chirality is one of the most important types of steric information in nature.

A sequential Ugi–Smiles/transition-metal-free endo-dig Conia–ene cyclization: the selective synthesis of saccharin substituted 2,5-dihydropyrroles

A convenient, transition-metal-free access to a series of unprecedented saccharin substituted 2,5-dihydropyrroles is reported.

Stereoselective Asymmetric Synthesis of Pyrrolidines with Vicinal Stereocenters Using a Memory of Chirality-Assisted Intramolecular SN2' Reaction

An efficient strategy for the asymmetric synthesis of pyrrolidines with vicinal quaternary-tertiary or quaternary-quaternary stereocenters was established. A "memory of chirality" intramolecular S_N2' reaction of α-amino ester enolates with allylic halides provided a functionalized pyrrolidine with excellent dia- and enantioselectivity. This method features construction of stereochemically enriched pyrrolidines in a single operation through the influence of a single chiral center presented in substrates.