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Cycloaddition Reactions of Heterocumulenes, XXII.- Reactions of Thioketenes with 3-Dimethylamino-2H-azirines
Schaumann, Ernst,Grabley, Susanne,Grabley, Fritz-Feo,Kausch, Erwin,Adiwidjaja, Gunadi
, p. 277 - 289 (2007/10/02)
Thioketenes 1 effect C=N cleavage in the aminoazirine 2 to give the dipoles 5a-c or the ketenimines 6d-h, depending on the substituents of the thioketene system.Except for 6d, hydrolysis of 6 proceeds via 5 to afford 2-thiazolin-5-ones 7 and α-carbamoylthioamides 9.Thermally the ketenimines 6 isomerize in a formal -sigmatropic shift to furnish ketene S,N-acetals 8.Also in the 2-monosubstituted azirine 11, 1,3-bond cleavage occurs with 1 and yields thiazoles 13.In contrast, the 2-phenylazirine 16 opens at the 1,2-bond in the reaction with 1, and leads to 2-thiazo lin-4-ones 20A via 19.The constitution of 20c was proved by an X-ray structural analysis.
