ジフェン酸類から3, 4-ベンゾクマリン類の合成

概要

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An improved preparative method of 3, 4-benzocoumarins was presented. Thus, 3, 4-benzocoumarin (2) was obtained in a good yield (87%) from diphenic acid (1) (0.01 mol) by refluxing for 6 hours with hydrogen peroxide (3) (0.1 mol) in dil. sulfuric acid (0.4 N; 250 cc). The similar reaction of 4-nitro- (1) gave 2-nitro- (2) as the sole product, from which the corresponding amino and acetylamino compounds were derived. As a catalyst, sulfuric acid was remarkably effective and the optimum concentration was found to be ca. 0.4 N, whereas basic additives showed no advantage. Some water-miscible organic solvents were also examined, but provided no advantage.<BR>Monoperdiphenic acid was prepared in a yield of 70% from diphenic anhydride by treating with alkaline solution of (3) at -10-15°C. The peracid yielded a mixture of (1) and (2) by heating in an aq. solution and these results seem to shed some light on the mechanism of the above reaction.
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