Palladium-Catalyzed Selective B(3)-H Arylation Of O-Carboranes With Arylboronic Acid

o-Carboranes,a kind of carbon-boron cluster compounds with an icosahedral cage structure,have very broad development prospects in military industries,coordination chemistry,luminescent materials and other fields due to their three dimensional super-aromaticity,excellent thermal and chemical stability.Therefore,the research on the efficient synthesis of o-carborane derivatives is of great significance to promote the development of carborane chemistry.In contrast to well-developed functionalization of C-H vertices of o-carboranes,the selective functionalization of ten extremely similar B-H vertices is currently the focus of attention in the field of carborane chemistry.The functionalization of the most electron-deficient B（3,6）-H vertex continues to be a challenging work.Based on this,the thesis has carried out the research on the"vertex-selective arylation of o-carboranes".The main research contents and research results are as follows:A new method for selective B（3）-H functionalization of o-carborane at room temperature has been reported in this manuscript.First,a pyridine group with strong coordination effect,has been introduced at a C-H vertex as the directing group,followed by a palladium-catalyzed selective B（3）-H arylation with arylboronic acids to afford arylation products.This method has good universality.A variety of arylboronic acids with both electron-donating and electron-withdrawing substituents at the ortho,meta,and para positions were tolerated in this reaction.Different types of polysubstituted o-carboranes derivatives,including 1-monosubstituted-,1,2-disubstituted-and1,2,3-trisubstituted-o-carborane substrates,could also participate in the reaction to give the corresponding products in high yields.The structure of all products was distinguished by NMR spectra(¹H,¹³C,¹¹B,¹¹B{¹H}and ¹⁹F),high resolution mass spectra,elemental analyses,single-crystal X-ray diffraction and melting point test.A plausible reaction mechanism was proposed.This method provides a new strategy for the synthesis of functionalized o-carborane derivatives.