ChemInform Abstract: Reactions of Isothiocyanates with Organometallic Reagents. Part 5. New Approach to Aminothiophene Syntheses.

Abstract

Reactions of Isothiocyanates with Organometallic Reagents. Part 5. New Approach to Aminothiophene Syntheses. --(BRANDSMA, L.; TARASOVA, O. A.; VVEDENSKII, V. YU.; DE JONG, R. L. P.; VERKRUIJSSE, H. D.; KLYBA, L. V.; NEDOLYA, N. A.; TROFIMOV, B. A.; Russ.

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

“…Nedolya Unsubstituted and 5-substituted 2-thiopheneamines 83 were obtained likewise from isothiocyanates and 1-lithiated 1-propynes 84 [99,251] The reactions of α-lithiated methoxy-and (methyl sulfanyl)allenes with isothiocyanates lead to N-alkyl-85 and N,N-dialkyl-3-methoxy(methylthio)-2-thiopheneamines 86 [99,252]. In the case of 3-methoxy-2-thiopheneamines 85 experimental evidence was obtained for amine-imine tautomerism in 2-thiopheneamines for the first time [99,252,253]. Alcoholysis of the acetal 90 instead of 5-hydroxy-2-thiopheneamine 91 or its keto tautomers 92 led unexpectedly to the ester of 4-amino-4-thioxobutyric acid 93 [254].…”

“…A. Tarasova, et al) as a new general approach to the synthesis of 2-thiopheneamines[79,99,101,233,[251][252][253][254][255][256]. 5-tert-Butyl-2-thiopheneamines 82 were synthesized for the first time by intramolecular cyclization of the adducts of lithiated tert-butylallene and isothiocyanates[99,251].…”

Reactions of heterocumulenes with organometallic reagents: XVIII. Quantum-chemical study on the mechanisms of formation of thiophene ring from lithium and potassium buta-2,3-dienimidothioates

“…Replacement of lithium cation in intermediate II′ by potassium (via addition of powdered potassium tert-butoxide to the reaction mixture) increases the yield of thiophenamine III to 75% (Scheme 1, ii) [9]. Likewise, the reaction is most likely to occur through…”

“…It was presumed that the reaction involves intramolecular cyclization of lithium butadienimidothioate II′A (S-centered azatriene anion) with formation of iminothienyl anion IV′ with lithium as counterion and subsequent isomerization of IV′ into lithium thienylamide V′. Treatment of the latter with methyl iodide yields thiophenamine III (Scheme 2).Replacement of lithium cation in intermediate II′ by potassium (via addition of powdered potassium tert-butoxide to the reaction mixture) increases the yield of thiophenamine III to 75% (Scheme 1, ii) [9]. Likewise, the reaction is most likely to occur through…”

“…We were the first to show that acetylene, allene, and butadiene carbanions and heterocumulenes, primarily isothiocyanates and isocyanates, generated in situ are universal building blocks for generally one-pot assembly of most fundamental aza, oxa, and thia heterocycles [7], including thiophehes [7][8][9]. While developing studies in this field, we found that the yield of thiopene considerably depends not only on the reactant structure and reaction conditions, but also on the nature of counterion.…”