Allyl esters of 3-carboxylcoumarins undergo facile decarboxylative coupling at just 25−50 °C. This represents the first extension of decarboxylative C−C bond-forming reactions to the coupling of aromatics with sp3-hybridized electrophiles. Finally, the same concept can be applied to the sp2−sp3 couplings of pyrones and flavones. Thus, a variety of biologically important heteroaromatics can be readily
3-羧基香豆素的烯丙酯在 25−50 °C 下即可轻松脱羧偶联。这代表了脱羧CC键形成反应首次扩展到芳香族化合物与sp 3杂化亲电子试剂的偶联。最后,相同的概念可以应用于吡喃酮和黄酮的 sp 2 -sp 3偶联。因此,多种生物学上重要的杂芳族化合物可以很容易地官能化,而不需要更标准的交叉偶联反应通常需要的强碱或化学计量的有机金属化合物。
Sydnone-coumarins as clickable turn-on fluorescent sensors for molecular imaging
Copper-catalyzed and copper-free sydnone–alkyne cycloaddition reactions have emerged as complementary click tools for chemical biology but their use in bioorthogonal labeling is still in its infancy. Herein, combinations of alkynes and coumarin-sydnones were screened for their ability to generate pyrazole products displaying strong fluoroscence enhancement compared to reactants. One sydnone was identified