Background: Silicon rhodamines are of particular interest because of their advantageous dye properties (fluorescence- and biostability, quantum efficiency, tolerance to photobleaching). Therefore, silicon rhodamines find frequent application in STED (stimulated emission depletion) microscopy, as sensor molecules for, e.g., ions and as fluorophores for the optical imaging of tumors. Different strategies were already employed for their synthesis. Because of just three known literature examples in which Suzuki–Miyaura cross couplings gave access to silicon rhodamines in poor to moderate yields, we wanted to improve these first valuable experimental results.
Results: The preparation of the xanthene triflate was enhanced and several boron sources were screened to find the optimal coupling partner. After optimization of the palladium catalyst, different substituted boroxines were assessed to explore the scope of the Pd-catalyzed cross-coupling reaction.
Conclusions: A number of silicon rhodamines were synthesized under the optimized conditions in up to 91% yield without the necessity of HPLC purification. Moreover, silicon rhodamines functionalized with free acid moieties are directly accessible in contrast to previously described methods.
背景:硅罗丹明因其有利的染料特性(荧光和生物稳定性、量子效率、对光漂白的耐受性)而特别受到关注。因此,硅罗丹明常用于STED(受激发射耗尽)显微镜,作为例如离子和肿瘤光学成像的荧光团的传感器分子。已经采用了不同的策略来合成它们。因为在仅有的三个已知文献实例中,铃木-宫浦交叉偶联以较差到中等产率得到了硅罗丹明,我们想要改进这些初步有价值的实验结果。
结果:提高了xanthene triflate的制备,并筛选了多种硼源以找到最佳的偶联伴侣。在优化了钯催化剂之后,评估了不同的取代硼氧烷来探索钯催化的交叉偶联反应的范围。
结论:在优化的条件下合成了多种硅罗丹明,产率高达91%,无需HPLC纯化。此外,与先前描述的方法相比,带有自由酸基团的功能化硅罗丹明可以直接获得。