A. Zonouzi, D. Kazemi, M. Nezamabadi
Jun 1, 2006
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0
Influential Citations
7
Citations
Journal
Organic Preparations and Procedures International
Abstract
2-Amino-4H-pyrans are an important group of compounds with various applications. Some have been shown to exhibit biological activity and have been used as anti-cancer, antihypertensive and coronary dilating agents.'" They are also important intermediates in organic ~ynthesis .~~ A number of different methods for the synthesis of 2-amino-4H-pyran derivatives have been described.10"6 We now report a one-pot synthesis of dimethyl, diethyl and di-tertbutyl-2-(tert-butylamino)-5-benzoyl-6-phenyl-4H-pyran-3,4-dicarboxylate (5a-c) and of dimethyl, diethyl, di-tert-butyl-2-(cyclohexylamino)-5-benzoyl-~phenyl-4H-pyran-3,4-dicarboxylates (5d-f) in fairly high yields. One of us has already reported the reaction between alkyl isocyanides (1) and dialkyl acetylenedicarboxylates (2) in the presence of 1,3-diphenylpropane1,3-dione to afford the highly functionalid ketenimines 3." Reflux of these ketenimines in benzene for 2-3 days led only enolization to compounds 4 without cyclization. By changing the addition sequence of the reactants and using the suitable base, we have achieved the preparation of 2-amino-4H-pyrans (5a-f) in good yields (Scheme I ) . RN=C + R'O&C=CC&R' 2