with BF3–etherate had considerable stability. The reaction, monitored by EPR studies at −25°C, occurred by free radical intermediates. EIMS further revealed a C40H56BF3 intermediate. The detailed structure of the charge delocalised β,β-carotene dication was established by COSY, HSQC, HMBC and 1D and 2D ROESY NMR techniques (600 MHz, CDCl3, −25°C) leading to complete assignments of 1H and 13C chemical
β,
β-胡萝卜素双阳离子(λ最大通过治疗β,
β-胡萝卜素与BF制备在室温下985纳米)3 -etherate有相当的稳定性。该反应由自由基中间体在-25°C下通过EPR研究监控。EIMS进一步揭示了C 40 H 56 BF 3中间体。通过COSY,HSQC,HMBC和1D和2D ROESY NMR技术(600
MHz,CDCl 3,-25°C)建立了电荷离域的β,
β-胡萝卜素指示剂的详细结构,从而完成了1 H和13 C的完全分配
化学位移和3 J H,H耦合常数。相对于β,
β-胡萝卜素,观察到相当大的下场位移。结果与主要在C-5–C-9和C-5'–C-9'区中的电荷离域化以及在C-13–C-13'中部区域中的向后移动双键相符。讨论了两个离域电荷对
化学位移(电荷分布)和键距(3 J H,H)的影响。