Regioselective synthesis of azetidines or pyrrolidines by selenium-induced cyclization of secondary homoallylic amines

Electrochemically chalcogenative annulation enabled construction of functionalized saturated N-heterocycles

An efficient chalcogenative annulation strategy for constructing functionalized saturated N-heterocycles from unactivated alkenes with dichalcogenides under electrochemical conditions has been presented. This protocol is applicable to mono-, di- or tri-substituted alkenes, providing a straightforward pathway to aziridines, azetidines, pyrrolidines, and piperidines with high regioselectivity. Moreover, the strategy is qualified to realize the oxychalcogenation of alkenes as well.

Recent strategies used in the synthesis of saturated four-membered heterocycles

The importance and prevalance of O-, N-, and S-atom containing saturated four-membered ring motifs in biologically active molecules and potential therapeutics continues to drive efforts in their efficient synthetic preparation. In this review, general and recent strategies for the synthesis of these heterocycles are presented. Due to the limited potential bond disconnections, retrosynthetic strategies are broadly limited to cyclizations and cycloadditions. Nonetheless, diverse approaches for accessing cyclization precursors have been developed, ranging from nucleophilic substitution to C-H functionalization. Innovative methods for substrate activation have been developed for cycloadditions under photochemical and thermal conditions. Advances in accessing oxetanes, azetidines, and thietanes remain active areas of research with continued breakthroughs anticipated to enable future applications.

Selenocyclization by formation of carbon-nitrogen bonds

Selenium promoted cyclization of unsaturated substrates containing internal nitrogen nucleophiles, such as different amines and amides, including the examples of its application in the synthesis of more complex polycyclic compounds is reviewed. Selenocyclization reactions of some more specific polyfunctional substrates, like Biginelli hybrids and hydantoins, are also covered.

Diamine-mediated N2-selective β-selenoalkylation of triazoles with alkenes

A N2-selective β-selenoalkylation of 1,2,3-triazoles with alkenes mediated by diamines has been developed. The reaction proceeds presumably via the interaction of diamines with both the triazole moiety and selenium/alkene complex to construct a U-shaped reaction intermediate. This activation mode will block the N1 position on triazoles and thus favor the N2-selective selenoamination. This stereospecific anti-addition method enables an efficient N2-selective β-selenoalkylation of 1,2,3-triazoles under mild and open-air conditions and might find applications in the synthesis of biologically active molecules.

Efficient Protocol for Synthesis of β-Hydroxy(alkoxy)selenides via Electrochemical Iodide-Catalyzed Oxyselenation of Styrene Derivatives with Dialkyl(aryl)diselenides

An efficient protocol for the synthesis of β-hydroxy(alkoxy)selenides was developed through the electrochemical iodide-catalyzed oxyselenation of styrene derivatives with dialkyl(aryl)diselenides under mild reaction conditions. Mechanistic studies showed that the cation I+ is involved during the whole process, and accelerates the formation of seleniranium ion via substitution and addition reaction with dialkyl(aryl)diselenides and styrene derivatives. The corresponding products are formed in good to excellent yields. This electrochemical oxyselenation provides an efficient strategy for difunctionalization of alkenes.

Facile and Green Synthesis of Saturated Cyclic Amines

Single-nitrogen containing saturated cyclic amines are an important part of both natural and synthetic bioactive compounds. A number of methodologies have been developed for the synthesis of aziridines, azetidines, pyrrolidines, piperidines, azepanes and azocanes. This review highlights some facile and green synthetic routes for the synthesis of unsubstituted, multisubstituted and highly functionalized saturated cyclic amines including one-pot, microwave assisted, metal-free, solvent-free and in aqueous media.