Synthesis of a library of "lead-like" γ-lactams by a one pot, four-component reaction

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.

Mechanistic Investigation of Castagnoli-Cushman Multicomponent Reactions Leading to a Three-Component Synthesis of Dihydroisoquinolones

The mechanisms for the three- and four-component variants of the Castagnoli-Cushman reaction (CCR) have been investigated. A series of crossover experiments were conducted to probe the structure and reactivity of known amide-acid intermediates for the three- and four-component variants of the CCR (3CR and 4CR, respectively). Control experiments paired with in situ reaction monitoring with infrared spectroscopy for the 4CR align with a mechanism in which amide-acids derived from maleic anhydride can reversibly form free amine and cyclic anhydride. Although this equilibrium is unfavorable, the aldehyde present can trap the primary amine through imine formation and react with the enol form of the anhydride through a Mannich-like mechanism. This detailed mechanistic investigation coupled with additional crossover experiments supports an analogous mechanism for the 3CR and has led to the elucidation of new 3CR conditions with homophthalic anhydride, amines, and aldehydes for the formation of dihydroisoquinolones in good yields and excellent diastereoselectivity. This work represents the culmination of more than a decade of mechanistic speculation for the 3- and 4CR, enabling the design of new multicomponent reactions that exploit this novel mechanism.

Diastereoselective Base-Catalyzed Formal [4 + 2] Cycloadditions of N-Sulfonyl Imines and Cyclic Anhydrides

A diastereoselective base-catalyzed Mannich reaction of cyclic, enolizable anhydrides and N-sulfonyl imines for the synthesis of δ-lactams is reported. This anhydride Mannich reaction tolerates imines derived from aryl and enolizable aldehydes. A base-catalyzed product epimerization pathway ensures high anti diastereoselectivity in aryl and achiral enolizable imines.

The first solvent-free synthesis of privileged γ- and δ-lactams via the Castagnoli–Cushman reaction

The first solvent-free protocol for the atom-economical Castagnoli–Cushman reaction is reported.