The reaction of 2,1-benzisothiazoline-3-thiones with acetylenic reagents

Abstract

. Can. J. Chem. 65, 1247Chem. 65, (1987. N-Methyl-2,l-benzisothiazoline-3-thione reacts with acetylene esters to form o-iminobenzoquinone methides which either form diazocines 2 by head-to-tail dimerisation, or react further with the acetylenic ester forming diadducts. With phenylacetylene a 1,2-dithiolo[2,3-b]2,1-benzisothiazole structure is obtained by rearrangement of an initial adduct. Related thiones and acetylenes react similarly but in poorer yields. The crystal and molecular structuresf the diazocine were determined by single crystal X-ray diffractometry techniques: The compound crystallizes in space group P 1 with unit cell dimensions a = 7.9465(10), b = 13.6421(14), c = 13.9183(18) A, a = 82.38(1), P = 83.67(1), y = 85.77(1) deg, and Z = 2. The structure was solved by direct methods and refined to an R value of 0.056 for 3037 observed reflections. The structure consists of molecules of 2a which have an approximate C2 axis passing through the center of the eight-membered ring. Deviations from true symmetry result from internal ring strain, lone pair-lone pair repulsions, and packing effects. [Traduit par la revue]

Structure of an 8a-trifluoromethyl-8aH-cycloheptatrieno[b]pyrrole

“…Stavaux, Lozac'h & Hordvik, 1985) and bis(dithiolotetrahydrodibenzodiazocine) (McKinnon, Secco & Duncan, 1987) with C--N distances of 1.29 and 1.42/~, respectively. The corresponding negative charge is expected to be located at the S(3) atom as the length of the C(2)--S(3) bond [1.72 (1) /~] indicates a single bond.…”

Synthesis of Thienothiopyranthiones by a New Molecular Rearrangement

“…The first cycloaddition is accompanied by heterocyclic ring opening to give a 1:1 adduct (as in Scheme ), which under more vigorous conditions adds a second alkyne in a Diels−Alder reaction to give a 1,4-dihydrothiopyran 1 …”

4,5-Dichloro-1,2-dithiole-3-thione in the synthesis of benzimidazole, benzoxazole and benzothiazole derivatives of 1,3-dithioles

“…[2][3][4] The first cycloaddition was accomplished by heterocyclic ring opening to give 1,3-dithiols (e.g., 3 in Scheme 1), which sometimes add a second alkyne in a Diels-Alder reaction to give 1,4-dihydrothiopyran. 5,6 An attractive starting material could be 4,5-dichloro-1,2-dithiole-3-thione 2, which is readily prepared from 3,4,5-trichloro-1,2-dithiolium chloride, 7 and in which the 5-chlorine is activated towards nucleophilic displacement. However if 2, reacted, as in Scheme 1, with DMAD, for example, it would generate dimethyl 2-(1,2-dichloro-2-thioxoethylidene)-1,3-dithiole-4,5-dicarboxylate 3, which is expected to be more reactive towards nucleophiles.…”