Synthesis And Application Of Fluorescent-labeled Organic Nitrogen Borane Catalyst

The four-coordinate organic nitrogen borane has attracted much attention in organoborone chemistry.It has been widely used in material science and life science.It can be gradually divided into two sub-filed.One is a fluorescent-labeled four-coordinate organic nitrogen borane,while the other is four-coordinate organic nitrogen borane catalyst.The former as one of the efficient fluorescence dyes with unique luminescence and good thermal stability,has attracted increasing attention.However,there are many deficiencies,including limited synthetic methods and varieties,long synthetic steps,harsh synthetic conditions,expensive raw materials,the lower yields,and no report with their catalytic performance is disclosed.And the later as frustrated Lewis pair can activate some small molecular compounds,for instance,H2,NO,SO2,alkenes and alkyne.It can be also used as an efficient nonmetal catalyst to avoid the environmental pollution caused by transition metal catalysts.However,it also has suffered from shortcomings:(1)In most cases,the dosage of catalyst is relatively large and the recycling process is difficult,especially in homogeneous catalysis;(2)it's difficult to effectively detect the trace remaining catalyst in the product by simpe UV analysis or TLC analysis,particularly in the drug synthesis.Therefore,the design and synthesis of organic nitrogen borane catalysts with stable structure,high catalytic performance and high fluorescence has highly demanding.In this paper,a series of stable fluorescent-labeled organic nitrogen borane catalyst were synthesized by iodine-catalyzed fluoroamides,and we demonstrated their composition,structure and physical or chemical properties.The catalytic performance of these catalysts are evaluated by Hantzsch reaction,Mannich reaction,synthesis 1,2-disubstituted benzimidazoles and(E)-?,?-unsaturated ketones.In addition,we also designed and synthesized the racemic chiral boron compounds based on 2,2,2-trifluoro-N-(quinolin-8-yl)acetamide.The results and conclusions are as follows:1.A series of stable fluorescent-labeled organic nitrogen borane catalyst were synthesized by treatment of the 2,2,2-trifluoro-N-(quinolin-8-yl)acetamide and sodium tetraphenylborate in the presence of iodine as catalyst.Their structures were characterized by Nuclear Magnetic Resonance(NMR),Mass Spectrometry(MS),High Mass Spectrometry(HRMS),single-crystal X-ray diffraction,Thermo-Gravimetric-Differential Thermal Analyz(TG-DTA),fluorescence detection and Discrete Fourier Transform(DFT).We found that the strength of the N?B coordination bond would be influenced by introducing the organic groups.The fluorescence data shows that the introduction of ?-conjugate groups in ligands increased the conjugated degree of the whole molecule and red-shifted the emission peak is apprear.In addition,it exhibits good thermal stability.2.We investigated the catalytic properties of fluorescent-labeled organic nitrogen borane catalysts by Hantzsch reaction.The results show that the stronger the electron withdrawing ability of the organic groups connected to the boron is,the higher the catalytic performance of the corresponding complexes to the Hantzsch reaction will be,which is consistent with the strength of the N-B coordination bond.In addition,we found that the optimal catalytic performance of catalyst 3s exhibit excellent chemical selectivity and stereoselectivity in the synthesis of benzimidazole derivatives and(E)-?,?-unsaturated carbonyl compounds,Mannich reactions.Duing to the presence of strong fluorescence in catalyst,it can be detected by 365nm UV lamp even at lower concentration.This provides a fast and simple detection method to detect the residual of the catalyst in the organic synthesis,which has high potential in pharmaceutical syntheiss.3.Based on the electrophilic properties of boron,we synthesized a novel racemic chiral fluorescent organic nitrogen borane by adding different organic acids in the previous reaction system.Their structures were characterized by Nuclear Magnetic Resonance(NMR),Mass Spectrometry(MS),High Mass Spectrometry(HRMS),single-crystal X-ray diffraction,Thermo-Gravimetric-Differential Thermal Analyz(TG-DTA),fluorescence detection.