Photoactivation of Amino-Substituted 1,4-Benzoquinones for Release of Carboxylate and Phenolate Leaving Groups Using Visible Light
作者:Yugang Chen、Mark G. Steinmetz
DOI:10.1021/jo060790g
日期:2006.8.1
a dark reaction. Lifetimes for elimination of 4-YC6H4OH in 30% phosphate buffer in CD3CN (pD 7) at 17 °C are 13.1, 0.54, and 0.13 h for Y = H, CF3, and CN, respectively, and the linear equation log k (h-1) = 0.998(−pKa) + 8.80 gives a best fit to the data. Carboxylate leaving groups are rapidly eliminated upon photolysis of the quinones in aq CH3CN to produce an o-quinone methide intermediate that is
暴露于可见光后,2-吡咯烷基取代的3,6-二甲基-1,4-苯醌光环化生成苯并恶唑啉,其在CH 2 Cl 2中的量子产率为0.07-0.10 ,在CH 3 CN中的量子产率为0.02-0.04 ,且<0.01在30%CH 3 CN水溶液中。羧酸盐或苯酚盐的离去基团通过与醌的5-羟甲基偶合而结合,光环化作用得到苯并恶唑啉,这些苯并恶唑啉在黑暗反应中消除了离去基团。Y = H,CF 3和CN时,在17°C下消除CD 3 CN(pD 7)中30%磷酸盐缓冲液中的4-YC 6 H 4 OH的寿命分别为13.1,h,0.54和0.13h。线性方程log k(h- 1)= 0.998(-p ķ一)+ 8.80给出的最佳拟合到数据。在CH 3 CN中对醌进行光解后,羧酸酯离去基团会快速消除,从而生成邻醌甲基化物中间体,该中间体可通过4 + 2环加成与未反应的起始原料或添加的3-(二甲基氨基)-5,5-二甲