Sulfur-Alkyne Cyclizations for Formation of Dihydrothiophenes and Annulated Thiophenes

Abstract

Cycloisomerization of homopropargylic thiols to dihydrothiophenes is promoted by group VI metal carbonyls. Related thiacyclization transformations under basic and radical conditions are also described, including regioselective formation of benzothiophenes from aryl methyl sulfides and alkynes.

Density Functional Study of Mo-Carbonyl-Catalyzed Alkynol Cycloisomerization: Comparison with W-Catalyzed Reaction

“…The calculated results are collected in Table 1. A comparison of the energetics of the reactions M(CO) 6 → M(CO) 5 + CO and M(CO) 5 → M(CO) 4 + CO for M [unk] Mo and W shows that the first and second Mo -CO bond dissociation energies are 8.2 (8.0) and 8.7 (8.5) kcal/mol lower than the respective W-CO bond energies. The lower CO dissociation energies from the Mo-carbonyl complexes compared to W-analogues can be explained in terms of the fact that the relativistic effects significantly (more than 4d orbitals) destabilize the 5d orbitals, reduce the d π −π C−O* gap, and thus enhance the back-donation interaction in the case of tungsten.…”

“…Therefore, in this paper we investigated the energetics of the first and second CO dissociation from the Mo(CO) 6 , leading to Mo(CO) 5 and Mo(CO) 4 , respectively. The calculated results are collected in Table 1.…”

Metal Vinylidenes as Catalytic Species in Organic Reactions

“…[69] In this case, a stoichiometric amount of chromium hexacarbonyl was required to give the product in good yield (Scheme 49). The lack of catalytic processes is presumably due to the strong coordination of thiols to metals, thus leading to catalyst deactivation.…”

Synthesis of sulfur-containing heterocyclic compounds by cyclocondensation of acetylenic derivatives of anthraquinone with sodium sulfide

“…5,6 Thus, substituted benzo [b]thiophenes are estrogen-receptor modulators, thrombin inhibitors, anti-tumor and anti-inflammation agents. 1,2,7,8 Some of them are currently in pharmaceutical use or development. 7,8 In this connection, we considered it reasonable to study synthetic pathways to anthraquinones annelated by thiophene and other sulfur-containing rings.…”

“…There is much less information about sulfur-containing heterocyclic quinoid compounds. At the same time, the introduction of sulfur-containing rings into the structure of compounds often determines their pharmacological properties, [1][2][3] reduces side-effects of drugs, 4 or improves the technical characteristics of materials. 5,6 Thus, substituted benzo [b]thiophenes are estrogen-receptor modulators, thrombin inhibitors, anti-tumor and anti-inflammation agents.…”