An Unprecedented Synthesis of Eight-Membered-Ring Cyclic Thioimidic Esters by a Three-Component Reaction

Abstract

The three-component reaction of the isocyanides and dialkyl acetylenedicarboxylates or dibenzoylacetylene (DBA) in the presence of elemental sulfur is described. The reaction afforded the corresponding eight-membered cyclic thioimidic esters in good yields.

Unprecedented Synthesis of 2H,6H-1,5-Dithiocines Reinvestigated: A Structural Corrigendum Revealing Isothiazole-3(2H)-thiones

“…When we repeated the reactions of 1 with 2 in the presence of elemental sulfur as described, 9 identical substances were isolated. This was shown by the corresponding 1 H and 13 C NMR data ( Table 1).…”

“…Furthermore, they can be used as powerful Michael acceptors, and, in several cases, nucleophilic addition and formation of zwitterions are combined with other addition or (formal) cycloaddition steps to yield a variety of products by multicomponent reactions. 1 As part of our current studies 8 on unusual reactions of acetylenedicarboxylates, we noticed a report 9 of Alizadeh and Hosseinpour on the synthesis of 2H,6H-1,5-dithiocines 3 by treatment of isonitriles 1 with diesters or diketone 2 in the presence of elemental sulfur (Scheme 1). The products 3a-g were isolated as yellow powders in 80-92% yield and characterized by their sharp melting points (in the range of 95-147 °C), IR, 1 H NMR, 13 C NMR and MS data as well as by elemental analyses.…”

“…Comparison of the Data of Putative 2H,6H-1,5-Dithiocine 3a and Isothiazole-3-thione 6aSupposed product 3a from DMAD and tert-butyl isocyanide, ref 9. …”

“…Calcd for C 15 H 21 NO 4 S 2 (343.46): C, 52.45; H, 6.16; N, 4.08; S, 18.67. Found: C, 53.22; H, 6.29; N, 4.09; S, 17.29.Di-tert-butyl 2-tert-Butyl-3-thioxo-2H-isothiazole-4,5-dicarboxylate (6e)Yield: 0.48 g (1.28 mmol, 64%); orange-yellow crystals; mp 135 °C (Lit 9. 115-117 °C).…”

One-pot, three component reactions between isocyanides and dialkyl acetylenedicarboxylates in the presence of phenyl isocyanate: synthesis of dialkyl 2-(alkyl/arylimino)-2,5-dihydro-5-oxo-1-phenyl-1H-pyrrole-3,4-dicarboxylate

“…[8][9][10] The reaction of isocyanides with carbon-carbon triple bonds occurs in a stepwise manner through a zwitterionic intermediate, the ultimate fate of which appears to be dictated by the nature of original triple-bonded substrate. [11][12][13][14][15][16][17][18][19] In continuation of our interest in the application of isocyanides in heterocyclic synthesis, [20][21][22][23][24][25][26][27] we now report the reaction between alkyl/aryl isocyanides 1 and dialkyl acetylenedicarboxylate 2 in the presence of phenyl isocyanate. This one-pot, three component synthesis proceeded spontaneously at 38 ºC in CH 2 Cl 2 and leads to dialkyl 2-(alkyl/arylimino)-2,5-dihydro-5-oxo-1-phenyl-1H-pyrrole derivatives 3a-h (Scheme 1).…”