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Cyclizations of Substituted Benzylidene-3-alkenylamines:  Synthesis of the Tricyclic Core of the Martinellines

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journal contribution
posted on 14.01.2000, 00:00 by Kristine E. Frank, Jeffrey Aubé
The martinellines (1 and 2) are natural products that possess both interesting biological activity and chemical structure. During the investigation of a hetero Diels−Alder route to these molecules, alternate Lewis acid-dependent cyclizations of (2‘-amino-N-tert-butoxycarbonyl-5‘-chlorobenzylidene)-3-butenylamine (10) were observed. The reaction of a variety of imines with TMSOTf or TiCl4 led to the formation of different heterocycles including iminodibenzo[b,f][1,5]diazocines, hexahydropyrido[1,2-c]quinazolin-6-ones, tetrahydropyrrolo[1,2-c]quinazolin-5-ones, 2-arylpiperidines, and 2-arylpyrrolidines. Tetrahydropyrrolo[1,2-c]quinazolin-5-one 54, obtained via this new methodology, was used as an intermediate in the synthesis of the tricyclic ring system (65) of the martinellines.