Ring opening–ring closure of 4-phenyl-1,2-dithiole-3-thione: convenient route to novel thiinethione derivatives by the reaction with active methylene nitriles

Synthesis and Reactivity of 3H-1,2-dithiole-3-thiones

“…At the same time, in the case of the reaction of acetonitriles 107, which are structurally similar to compounds 88 under similar conditions, the amide group is involved in the reaction rather than the nitrile group, as might be expected from the previous scheme [102]. As a result, 2H-thiopyran-2-thiones 108 were isolated in high yields (Scheme 61).…”

“…After treatment of thione 102 with phosphonium salts 103 in the presence of lithium hydroxide in DMF, 1,3-dithiine 4-thione 104 was isolated as the main product (Scheme 59). Egyptian authors have shown that in the reaction of 4-phenyl-1,2-dithiole-3-thione with nitriles containing a reactive methylene group and with α,β-unsaturated nitriles, the sulfur atom is replaced by a C-C bond, while the carbon atom of the nitrile group and the adjacent carbon atom are included in the new cycle [102]. Thus, the reaction of 4-phenyl-1,2-dithiole-3-thione with 2-cyanomethyl-benzothiazole and -benzimidazole 105 in the presence of triethylamine gave products that the authors concluded to have the structure of imino-2H-thiopyran-2-thiones 106 (Scheme 60).…”

“…As a result, 2H-thiopyran-2-thiones 108 were isolated in high yields (Scheme 61). The reaction with conjugated nitriles 113 also involved the nitrile group and resulted in 2H-thiopyran-2-thiones 114 [102,104]. The reaction conditions are the same as in all previous transformations, i.e., refluxing in ethyl alcohol in the presence of a base (piperidine or triethylamine) (Scheme 64).…”

“…The reaction conditions are the same as in all previous transformations, i.e., refluxing in ethyl alcohol in the presence of a base (piperidine or triethylamine) (Scheme 64). If an acetamide group is present in a conjugated nitrile, then it is dehydrated into a nitrile group [102]. In all the cases described in this section, it is assumed that the cyclic sulfur atom at position 1 undergoes replacement.…”

Synthesis and synthetic applications of cyanoacetamides

“…Monocyclic six-membered rings with one hetero atom 3.1.5.1. Thiopyran (Thiine) derivatives A. Synthesis via Michael addition reactions The reaction of N-arylcyanoacetamide compounds 3 with 4-phenyl-3H-1,2-dithiole-3-thione 160 in ethanol at reflux in the presence of triethylamine as a basic catalyst afforded the thiopyran derivatives 163a-c via the intermediacy of 161 and 162 (Scheme 68, Table25) 108.…”