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A kind of method utilizing triazole salt and its conjugated base to catalyze the hydroboration of nitrogen heteroaryl ring compound
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A nitrogen heteroaromatic ring, conjugated base technology, applied in the field of organic synthesis, can solve the problems of metal residue and high cost
Active Publication Date: 2021-11-16
RENMIN UNIVERSITY OF CHINA
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Although there are currently some synthetic methods in which strong reducing agents are used to activate pyridine, as a conventional synthetic method for 1,2- or 1,4-DHP derivatives, subsequent use of relatively weak reducing agents such as silane and borane instead of the hydrogen reduction system are considered effective because they avoid the use of highly flammable and high-pressure hydrogen and avoid over-reduction to piperidine, but significant challenges remain with this system
[0003] In recent years, several schemes for the direct catalytic reduction of pyridine and nitrogen heterocycles have been developed. However, the early studies on such reactions mainly focused on metal-catalyzed systems, and mainly based on noble transition metals (ruthenium, rhodium, etc.), Therefore, there are problems of high cost and metal residues. It was not until 2015 that this metal-free catalyzed pyridine reductive hydroboration system was realized for the first time, but still requires 10% catalyst
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Embodiment 1
[0035] Embodiment 1, the preparation of triazole salt conjugate base system
[0036] according to figure 1 The flow chart shown prepares the triazolium salt conjugate base system. The specific operation is as follows:
[0037] Take the triazole salt (R 1 for Mes, R 2 for CH 3 ) (triazole salts were synthesized from known methods) (References: Bouffard, J.; Keitz, B.K.; Tonner, R.; Guisado-Barrios, G.; Frenking, G.; Groubbs, R.H.; Bertrand, G. , Organometallics 2011,30,2617-2627) 0.5mmol, and KHMDS solid 0.55mmol, under the protection of nitrogen, add THF 5ml at -78°C, react at low temperature for 1h, remove the solvent in vacuo, extract with toluene in the glove box, and drain the toluene to obtain the product.
[0039] image 3 It is the carbon nuclear magnetic resonance spectrum (13C-NMR) of the prepared triazolium salt conjugate base system....
Embodiment 2
[0042] Weigh 0.004mmol of the catalyst prepared in Example 1 above, 0.2mmol of pyrimidine, 0.44mmol of HBpin, and 0.7ml of deuterated benzene in a glove box, and react at 70°C for 12h. Drain the solvent to obtain the final product directly, and directly characterize it by NMR. Yield >99%.
[0044] Figure 5 It is the carbon nuclear magnetic resonance spectrum (13C-NMR) of the pyrimidine hydroboration product obtained.
[0045] It was confirmed that the final product was the target product.
Embodiment 3
[0047] In a glove box, 0.004 mmol of the catalyst prepared in Example 1 above, 0.2 mmol of acridine, 0.22 mmol of HBpin, and 0.7 ml of deuterated benzene were weighed, and reacted at 70°C for 12 hours. No need for post-processing, direct NMR characterization, yield >99%.
[0048] Figure 6 The proton nuclear magnetic resonance spectrum (1H-NMR) of the acridine hydroboration product prepared in the present invention.
[0049] Figure 7 It is the carbon nuclear magnetic resonance spectrum (13C-NMR) of the acridine hydroboration product prepared in the present invention.
[0050] It was confirmed that the final product was the target product.
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Abstract
The invention provides a method for catalyzing the hydroboration of nitrogen heteroaryl ring compounds by using triazole salts and their conjugated bases. The triazole salt and its conjugate base have structural formulas as shown in formulas I and II. The method for catalyzing the hydroboration of nitrogen heteroaromatic ring compounds by using triazole salts and their conjugate bases is: in the presence of triazole salts and their conjugate bases, the nitrogen heteroaromatic ring compounds are reacted with HBpin to obtain hydrogenboronchemical products. The nitrogen heteroaromatic compound is one of pyridine, acridine, pyrimidine, quinoline, isoquinoline, benzothiazole, pyrazine, triazine and derivatives thereof. The present invention uses triazolium salt and conjugate base system for the first time to catalyze the hydroboration reaction of nitrogen heteroaromatic ring compounds, abandons the traditional Lewis catalytic system, and realizes metal-free Lewis base catalyzed hydroboration of nitrogen heterocyclic compounds for the first time system, the amount of catalyst used is less and the yield is good.
Description
technical field [0001] The invention relates to the field of organic synthesis, in particular to a method for catalyzing the hydroboration of nitrogen heteroaryl ring compounds by using triazole salts and their conjugate bases. Background technique [0002] Reduced nitrogen heterocycles are important components of many pharmaceutical and agrochemical products. For example, the most common dihydropyridine (DHP) derivatives are ubiquitous in natural molecules, such as NADH and other biologically active substances (nicotinamide adenine di nucleotides), and molecules of great medicinal value, such as Hantzsch esters. Therefore, it is of great significance to develop effective synthetic methods of DHP and its derivatives. Although there are currently some synthetic methods in which strong reducing agents are used to activate pyridine, as a conventional synthetic method for 1,2- or 1,4-DHP derivatives, subsequent use of relatively weak reducing agents such as silane and borane in...
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