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

Svetlana V Amosova; Vladimir A Shagun; Nataliya A Makhaeva; Irina A Novokshonova; Vladimir A Potapov

doi:10.3390/molecules26216685

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

Molecules. 2021 Nov 4;26(21):6685. doi: 10.3390/molecules26216685.

Authors

Svetlana V Amosova¹, Vladimir A Shagun¹, Nataliya A Makhaeva¹, Irina A Novokshonova¹, Vladimir A Potapov¹

Affiliation

¹ Siberian Division of the Russian Academy of Sciences, A.E. Favorsky Irkutsk Institute of Chemistry, Favorsky Str. 1, 664033 Irkutsk, Russia.

Abstract

The results of quantum chemical and experimental studies of the reaction of 2-bromomethyl-1,3-thiaselenole with 1,3-benzothiazole-2-thiol made it possible to discover the unprecedented pathway of this reaction, which proceeds stepwise at three different centers of seleniranium intermediates. The first stage includes an attack of thiolate anion at the selenium atom of the seleniranium cation accompanied by ring opening with the formation of (Z)-2-[(1,3-benzothiazol-2-ylsulfanyl)selanyl]ethenyl vinyl sulfide, which is converted to six-membered heterocycle, 2-(2,3-dihydro-1,4-thiaselenin-2-ylsulfanyl)-1,3-benzothiazole, in a 99% yield. The latter compound undergoes rearrangement with ring contraction producing five-membered heterocycle, 2-[(1,3-thiaselenol-2-ylmethyl)sulfanyl]-1,3-benzothiazole, in a 99% yield (the thermodynamic product). The formation of 1,2-bis[(Z)-2-(vinylsulfanyl)ethenyl] diselenide is the result of the disproportionation of (Z)-2-[(1,3-benzothiazol-2-ylsulfanyl)selanyl]ethenyl vinyl sulfide. Thus, based on the quantum chemical and experimental studies, a regioselective synthesis of the reaction products in high yields was developed.

Keywords: 1,3-benzothiazole-2-thiol; 2,3-dihydro-1,4-thiaselenine; 2-bromomethyl-1,3-thiaselenole; rearrangement; seleniranium cation; vinyl sulfides.