- Cycloaddition Reactions of Cyclic Ketene-N,S-Acetals
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Reaction of 3,6-diphenyl-, 3,6-bis(2-pyridyl)- and the unsubstituted 1,2,4,5-tetrazine with 4,5-dihydro-1-methyl-2-(methylthio)pyrrole (2) and 1-methyl-2-(methylthio)-4,5,6,7-tetrahydroazepine (3) gives 4,7-di-R-2,3-dihydro-1-methylpyrrolopyridazine (4, R = phenyl, 2-pyridyl, hydrogen) and 6,9-di-R-1-methyl-2,3,4,5-tetrahydropyridazinoazepine (5), R = phenyl, 2-pyridyl, hydrogen), respectively, in reasonable to good yields.The compounds 4 (R = phenyl, hydrogen) are converted into their corresponding 1-methylpyrrolo-pyridazines 6 by reaction with potassium permanganate in butanone.Reaction of 3-phenyl-1,2,4,5-tetrazine with 2 and 3 leads to the exclusive formation of the 7-phenyl isomer 4d and 9-phenyl isomes 5d, respectively, indicating that the cycloaddition is regiospecific.The mechanism is discussed.
- Marcelis, Antonius T. M.,Plas, Henk C. van der
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p. 545 - 548
(2007/10/02)
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- Lactam Acetals: Potential Enamine Synthons in Heterocyclic Synthesis, 2. The Lactam Acetal/Ketene N,O-Acetal System in -Diels-Alder Reaction with Inverse Electron Demand
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Lactam acetals 1 can be regarded as a source of the electron rich cyclic ketene N,O-acetals 2.Their regiospecific -Diels-Alder reaction with inverse electron demand with the tetrazine 3 or triazine 5 under subsequent elimination of alcohol yields a
- Moehrle, Hans,Dwuletzki, Heinz
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p. 3600 - 3606
(2007/10/02)
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