Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

Abstract

The reaction of 2-(bromomethyl)-1,3-thiaselenole with potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on the generation of sodium 1,3-thiaselenol-2-ylmethylselenolate from 1,3-thiaselenol-2-ylmethyl selenocyanate or bis(1,3-thiaselenol-2-ylmethyl) diselenide followed by nucleophilic substitution reactions. Sodium 1,3-thiaselenol-2-ylmethylselenolate underwent nucleophilic addition to alkyl propiolates in a regio- and stereoselective manner affording 1,3-thiaselenol-2-ylmethyl vinyl selenides in high yields predominantly with Z-configuration. Not a single representative of the 1,3-thiaselenol-2-ylmethyl selenide scaffold has been previously described in the literature.

Quantum Chemical and Experimental Studies of an Unprecedented Reaction Pathway of Nucleophilic Substitution of 2-Bromomethyl-1,3-thiaselenole with 1,3-Benzothiazole-2-thiol Proceeding Stepwise at Three Different Centers of Seleniranium Intermediates

“…The present work is a necessary continuation of pioneering studies of the new methodology of nucleophilic substitution at three different centers of seleniranium intermediates in reactions of 2-bromomethyl-1,3-thiaselenole (1) with nucleophilic reagents (Scheme 1) [57][58][59][60][61]. The analysis of the data includes a comparison with the previously obtained results on the reactions of 2-bromomethyl-1,3-thiaselenole with sulfur-centered nucleophiles [57][58][59][60].…”

“…It has been experimentally proven by 1 H−NMR monitoring that the reaction of thiaselenole 1 with thiol 2 is accompanied by rearrangement of 4 into 5 (acetonitrile, Li 2 CO 3 , r.t.), which proceeds via the intermediate seleniranium cation (Figure 4) [58]. Similarly, the reaction thiaselenole 1 with potassium selenocyanate proceeds via a rearrangement with ring expansion leading to six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (the kinetic product), which in turn undergoes rearrangement with ring contraction into 1,3-thiaselenol-2-ylmethyl selenocyanate (the thermodynamic product) [61]. The reaction of disproportionation of selanyl sulfide 3 with the formation of two symmetrical products, 1,2-bis[(Z)-2-(vinylsulfanyl)ethenyl] diselenide (6a) and bis(1,3benzothiazol-2-yl) disulfide (6b), was studied (Figure 5).…”

“…2-Bromomethyl-1,3-thiaselenole (1) in solutions exists in equilibrium with intermediate seleniranium cation, which determines its unusual chemical properties [57][58][59][60][61] (Scheme 1). The formation of intermediate seleniranium cation in nucleophilic substitution reactions of thiaselenole 1 with dithiocarbamates was supported by quantum chemical calculations [59].…”

Organic Selenocyanates: Rapid Advancements and Applicationsin the Field of Organic Chemistry

“…[14] Amosova and colleagues discovered a new reaction in 2020 by combining 2-bromomethyl-1,3-thiaselenole 21 with KÀ SeCN at 0 °C.This reaction led to a six-membered 2-selenocyanato-2,3dihydro-1,4-thiaselenine 22 in an 80% yield, which then performed a rearrangement and ring retraction to 2-(selenocyanatomethyl)-1,3-thiaselenole 23 in an 86% yield at room temperature. [15] The author proposed a reaction mechanism in which thiaselenole 21 reacts with potassium selenocyanate to form a seleniranium intermediate (21B), which then generates rearrangement to form a six-membered thiaselenine 22, which is then reconstructed to produce a five-membered 2- selenocyanatomethyl-1,3-thiaselenole 23. These rearrangements occur as a result of the selenocyanate anion's nucleophilic attack on two distinct C-atoms in the seleniranium intermediate 21B (Scheme 11).…”

“…These rearrangements occur as a result of the selenocyanate anion's nucleophilic attack on two distinct C-atoms in the seleniranium intermediate 21B (Scheme 11). [15] Additionally, the author implemented two effective approaches for the synthesis of novel 1,3-thiaselenol-2-ylmethylselanyl derivatives (24 a-24 e) using selenocyanate (23) and diselenides (26). Selenocyanate (23) and diselenide (26) were identified as the synthons of the 1,3-thiaselenol-2-ylmeth-ylselenolate anion, which was engaged in nucleophilic substitution reactions as well as regio-and stereoselective nucleophilic additions to activated acetylenes (25 a and 25 b).…”