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Popp, Tobias Alexander; Uhl, Edgar; Ong, Duc Nghia; Dittrich, Sebastian; Bracher, Franz (2016): A new approach to monoprotected 1,4-benzodiazepines via a one-pot N-deprotection/reductive cyclization procedure. In: Tetrahedron, Vol. 72, No. 13: pp. 1668-1674
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Abstract

A novel approach to 2,3,4,5-tetrahydro-1H-1,4-benzodiazepines starting from N-Boc-protected 2-aminobenzyl alcohols and N-nosyl-protected 2-aminoacetaldehyde dimethyl acetal is presented here. After connection of both building blocks under Mitsunobu conditions, a one-pot cyclization is accomplished with triethylsilane and trifluoroacetic acid. This conversion involves Boc deprotection and an intramolecular reductive N-alkylation. A consecutive methylation at N-1 can be accomplished by adding 1,3,5-trioxane to the reaction mixture. The resulting N4-monoprotected 1,4-benzodiazepines are versatile building blocks for the synthesis of variously substituted drug candidates. (C) 2016 Elsevier Ltd. All rights reserved.