Regioselective synthesis of 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones and 12H-benzopyrano[3,2-c][1]benzopyran-5-ones by radical cyclization
作者： K.C Majumdar , P.K Basu , P.P Mukhopadhyay , S Sarkar , S.K Ghosh
DOI: 10.1016/S0040-4020(03)00182-0
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摘要: Abstract 5-Hydroxy uracils or 4-hydroxy[1]benzopyran-2-ones were refluxed with 2-bromobenzyl bromides in acetone the presence of anhydrous potassium carbonate to afford a number 5-(2′-bromobenzyloxy) pyrimidine-2,4-dione (80–92%) 4-(2′-bromobenzyloxy) benzopyran-7-ones (70–82%) respectively. These then tri-n-butyltin chloride and sodium cyanoborohydride catalytic amount azobisisobutyronitrile (AIBN) for 3–4 h give 1H,3H,6H [2]benzopyrano[4,3-d]pyrimidine-2,4-diones (75–85%) 12H-benzopyrano[3,2-c][1]benzopyran-5-ones (70–85%)
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