- Thermolysis of Polyazapentadienes. Part 8. The formation of Pyrroles from 1,1-Dialkyl-5-aryl-1,5-diazapentadienes
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Flash vacuum pyrolysis of the 1,5-diazapentadienes (4)-(10) gave moderate yields of pyrroles together with quinolines, formed by electrocyclic ring closure with elimination.The pyrroles were formed by hydrogen transfer from an N-alkyl group, followed by cyclisation and final aromatisation of the resulting dihydropyrrole intermediate by free-radical cleavage.The mechanism of the hydrogen transfer and cyclisation is not known with certainty, but may involve diradicals or 1,5-dipolar intermediates.
- McNab, Hamish,Murray, M. Elizabeth-Ann
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p. 333 - 338
(2007/10/02)
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- Halogenated Ketenes. 38. Cycloaddition of α,β-Unsaturated Imines with Ketenes To Yield Both β- and δ-Lactams
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The cycloaddition of various types of α,β-unsaturated imines with diphenyl- and dichloroketenes yields both (2 + 2) and (4 + 2) cycloaddition products, i. e., β-lactams and δ-lactams, respectively.The cycloaddition products are dependent upon substitution in the imine and the ketene.The δ-lactams derived from dichloroketene are easily dehydrochlorinated to the corresponding 2-pyridones.All of the results are consistent with a two-step cycloaddition process involving a dipolar intermediate.
- Brady, William T.,Shieh, C. H.
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p. 2499 - 2502
(2007/10/02)
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