Abstract
A novel and simple method for the synthesis of functionalized 2-amino-3-cyano-4-chromones is reported. The title compounds were isolated after acylation of malononitrile with Nhydroxybenzotriazolyl acetylsalicylates, generated in situ by treating acetylsalicylic acid derivatives with N-hydroxybenzotriazole, followed by cyclization. The described one-pot methodology is characterized by short reaction times, high yields (68 to 77%), no side-products and provides chromones with a variety of substituents on the aromatic ring. The structure of the isolated compounds has been determined by means of H/C NMR and FT-IR Spectroscopy.
Highlights
Chromones (Figure 1) constitute one of the major classes of naturally occurring compounds, and interest in their chemistry continues unabated because of their usefulness as biologically active agents.[1 ]
1,3- diketones or equivalent intermediates catalyzed by strong acids or strong bases (VilsmeierHaack reaction).[13]. They have been prepared on a large scale by the Allan-Robinson synthesis involving acylation-rearrangement, and subsequent cyclization.[14]
This methodology has been followed in the synthesis of chromone derivatives with quaternary ammonium functionalities which show activity of cosmetic interest and for hair sustainability, as well as in the asymmetric synthesis of optically active 4-chromone derivatives.[15]
Summary
Chromones (Figure 1) constitute one of the major classes of naturally occurring compounds, and interest in their chemistry continues unabated because of their usefulness as biologically active agents.[1]. 1,3- diketones or equivalent intermediates catalyzed by strong acids or strong bases (VilsmeierHaack reaction).[13] They have been prepared on a large scale by the Allan-Robinson synthesis involving acylation-rearrangement, and subsequent cyclization.[14] This methodology has been followed in the synthesis of chromone derivatives with quaternary ammonium functionalities which show activity of cosmetic interest and for hair sustainability, as well as in the asymmetric synthesis of optically active 4-chromone derivatives.[15] In the Baker-Venkataraman synthesis,[16] internal Claisen condensation of 2-aryloxy-1-acetylarenes is employed as a key step. During the last few years we have been involved in the one-step synthesis of heterocycles22a, 22b employing N-hydroxybenzotriazole esters of α-amino or α-hydroxy acids as acylating agents of active methylene compounds to produce a wide variety of γ-amino22c or γhydroxy butenoates,22d which can be converted to five-membered heterocycles with biological interest. We employed the N-hydroxybenzotriazole methodology in the synthesis of 4-hydroxycoumarins by using a number of substituted acetyl salicylic acids as the precursors.22e
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