Reaction of 2-bromomethyl-1,3-thiaselenole with thiourea: en route to the first representatives of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines

Regio- and Stereoselective Synthesis of a Novel Family of Unsaturated Compounds with the S–Se Bond and Their Cyclization to 2,3-Dihydro-1,4-thiaselenines

“…In the case of fivemembered thiaselenole 1, the coupling constant of the olefinic protons of the SCH=CHSe group was 3 J H,H = 6.3 Hz. 32,33 The signals of the selenium atoms in 77 Se NMR spectra of the synthesized compounds manifested themselves in the region 373-496 ppm (selanyl sulfides 2a-k and 3a,b) and 193-227 ppm (heterocycles 4a-i). A comparative analysis of the 77 Se NMR data for selanyl sulfides 2a-k (Table 1) and alkyl vinyl selenides 43 showed that the formal replacement of the α-CH 2 group in alkyl moiety of alkyl vinyl selenides by the sulfur atom leads to considerable deshielding of the selenium atom.…”

“…The cyclization reaction proceeded smoothly under mild reaction condi- Compound 4 (R = Et) was obtained by catalysis of CF 3 CO 2 H in 90% yield. 33 Сompounds 4b and 4f were obtained by us earlier by an alternative method with lower yields under more severe conditions based on 2,3-dihydro-1,4-thiaselenine functionalized with isothiuronium group. 33 The driving force of this cyclization is the formation of thermodynamically more stable heterocyclic products.…”

“…33 Сompounds 4b and 4f were obtained by us earlier by an alternative method with lower yields under more severe conditions based on 2,3-dihydro-1,4-thiaselenine functionalized with isothiuronium group. 33 The driving force of this cyclization is the formation of thermodynamically more stable heterocyclic products. The reaction pathway of the acid-catalyzed cyclization can be rationalized as follows: the proton promotes the cleavage of the Se-S bond leading to the formation of the seleniranium cation A and thiol, which attacks the carbon atom of intermediate A with a break of the C-Se bond (Scheme 8).…”

“…Starting 2-bromomethyl-1,3-thiaselenole (1) was prepared from SeBr 2 and divinyl sulfide according to the previously described procedure. 33…”

“…[32][33][34][35][36][37][38][39][40][41][42] The reactions of thiaselenole 1 with various nucleophiles of different nature proceeded mainly at room temperature in MeCN, EtOH, DMSO, rarely in the presence of equimolar amounts of K 2 CO 3 leading to novel functionalized unsaturated oxygen-, nitrogen-and sulfur-containing compounds with the formation of new Se-S, Se-Se, Se-C, C-O, C-N, and C=C bonds (Scheme 1). [32][33][34][35][36][37][38][39][40][41][42] Here we report on the regio-and stereoselective synthesis of novel families of compounds based on reactions of thiaselenole 1 with organic thiols and dithiols. We found that the classical nucleophilic substitution at the C 3 carbon atom in thiaselenole 1 with thiols did not occur (Scheme 1).…”