水相中3,5-二芳基异噁唑衍生物的微波辐射合成

Microwave Irradiation Synthesis of 3,5-Diarylisoxazoles in Aqueous Solution

微波辐射下,以芳香醛和芳香酮为起始原料合成2,4,6-三芳基吡喃盐,在NaOH水溶液中与盐酸羟胺发生开环、缩环和脱苯甲酰基反应,一步生成3,5-二芳基异噁唑衍生物。考察了微波辐射功率和辐射时间对目标产物收率的影响,2,4,6-三芳基吡喃盐与盐酸羟胺反应生成3,5-二芳基异噁唑衍生物的最佳微波辐射功率为600W,辐射时间为8min,最大收率为83%。该法不仅避免了使用高氯酸造成的环境污染,而且以水作为反应介质,使后处理简便。该工艺具有操作安全、反应条件温和和产率高等优点,是一种环境友好的合成工艺。产物经元素分析、1HNMR和MS测试技术表征了其结构。

2,4,6-Triarylpyrylium salts were synthesized with aromatic aldehydes and aromatic ketones as starting materials.We succeeded in the conversion of these salts with hydroxylamine hydrochloride in water and synthesized the 3,5-diarylisoxazole derivatives under microwave irradiation.In comparison with literature method,the microwave approach shows the salient features of rapid reaction rates and significant energy saving,clean reaction conditions,enhancement in chemical yield,and nonuse of perchloric acid（70%）,which will result in cost saving and minimize safety concerns in the organic laboratory.In addition,the use of aqueous reaction conditions results in simple,environmentally friendly procedures.This rapid and easy technique coupled with water medium may contribute to the dream of Green Technology.The optimum reaction conditions were selected（P=600 W,time=8 min,yield 83%） and twelve compounds were synthesized via this procedure.The structures of the products were confirmed by elemental analysis,MS and 1H NMR spectroscopy.