Synthetic Studies on 2H-Thiopyran Compounds: A Reinvestigation of the Reaction Between Benzaldehydes and Sodium Sulfide
18 Nov 2009-Phosphorus Sulfur and Silicon and The Related Elements (Taylor & Francis Group)-Vol. 184, Iss: 12, pp 3199-3211
TL;DR: In this paper, the synthesis of 2H-thiopyran compounds from substituted benzaldehydes with sodium sulfide (Na2S·10H2O) in aqueous ethanol was carried out.
Abstract: An investigation regarding the synthesis of 2H-thiopyran compounds from substituted benzaldehydes with sodium sulfide (Na2S·10H2O) in aqueous ethanol was carried out. The structural elucidation of the products was performed by spectroscopic methods and in one example as X-ray crystallographic analysis. A plausible mechanistic pathway is also proposed that is entirely different from an earlier report.
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TL;DR: In this paper, a brief analysis of the current understanding of substituent perturbations in monosubstituted benzenes as determined by substituents induced carbon chemical shifts is presented.
Abstract: A brief analysis is presnted of the current understanding of substituent perturbations in monosubstituted benzenes as determined by substituent induced carbon chemical shifts. A critical tabulation of the four substituent chemical shifts is given for c. 700 monosubstituted benzenes.
458 citations
TL;DR: The cycloaddition of 2- or 2,3-substituted 1-thia- and 1 -thia-3-aza-4-dimethylamino-buta-1, 3-dienes with various dienophiles in the presence of a Lewis acid provides a rapid and diastereoselective access to the 3,4-dihydro-2H-thiopyran and 5,6-diphysine backbones as discussed by the authors.
Abstract: The cycloaddition of 2- or 2,3-substituted 1-thia- and 1-thia-3-aza-4-dimethylamino-buta-1,3-dienes with various dienophiles in the presence of a Lewis acid provides a rapid and diastereoselective access to the 3,4-dihydro-2H-thiopyran and 5,6-dihydro-4H-[1,3]thiazine backbones. The generally observed trans relationship between the two newly created strereogenic centres was demonstrated to be the expression of a thermodynamic control of the reaction. The use of chiral dienophile derived from chiral oxazolidin-2-ones allowed us to prepare enantiopure 5,6-dihydro-4H-[1,3]thiazines and 3,4-dihydro-2H-thiopyrans. In the asymmetric synthetic process the chiral auxiliary removal step was best accomplished in the presence of samarium triflate in methanol.
21 citations
TL;DR: In this paper, the synthesis of C18-juvenil hormone was studied using 4.4-Methyl-5,6-dihydro-2H-thiopyran and its dimer.
Abstract: 4-Methyl-5,6-dihydro-2H-thiopyran and its dimer (4) are used as structural units for the synthesis of C18-juvenil hormone.
11 citations
TL;DR: The hetero-Diels-Alder reaction of 3-dimethylamino-1-(2-thienyl)-2-propene-1-thione (diene) with substituted β-nitrostyrenes, as well as maleic and fumaric acids (dienophiles) yielded 3,4-dihydro-2H-thiopyran derivatives as discussed by the authors.
Abstract: The hetero-Diels-Alder reaction of 3-dimethylamino-1-(2-thienyl)-2-propene-1-thione (diene) with substituted β-nitrostyrenes, as well as maleic and fumaric acids (dienophiles) yielded 3,4-dihydro-2H-thiopyran derivatives. The treatment of some of those cycloadducts with acetic acid caused elimination of dimethylamine, affording stable 2H-thiopyrans. A reaction of the diene with maleic anhydride furnished a cycloadduct which underwent spontaneous rearrangement to form an N,N-dimethylamide derivative. Cycloadditions of the diene to maleimide, N-phenylmaleimide, maleic acid monoanilide, diethyl maleate, fumarate, and butenolide carried out in the presence of acetic anhydride were followed by elimination of dimethylamine under formation of stable 2H-thiopyran derivatives.
11 citations
TL;DR: In this paper, 2,6-Diphenyl and 2,phenyl-6-p-tolyl-4-thiopyrylidenemalomonitriles have been synthesized as f, g -unsaturated nitriles from the condensation of 2, 6-diphensyl with malononitrile.
Abstract: 2,6-Diphenyl and 2-phenyl-6-p-tolyl-4-thiopyrylidenemalomonitriles have been synthesized as f , g -unsaturated nitriles from the condensation of 2,6-diphenyl and 2-phenyl-6-p-tolyl-4H-thiopyran-4-thiones with malononitrile. Treatment of 4-thiopyrylidenemalononitriles with hydrazine hydrate, hydroxylamine hydrochloride, thiourea, thiosemicarbazide, or guanidine hydrochloride afforded the corresponding spirothiopyran derivatives of pyrazole, isoxazole, 1,3-thiazine or pyrimidine, respectively, while treatment with acetylacetone gave the corresponding spirothiopyran derivatives of pyran.
8 citations