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Highly Efficient Synthesis of Pyrazole Derivatives and5-(Isoxazol-3-yl) Pyrimidine Nucleosides

Author: WangJiLiang
Tutor: FanXueSen
School: Henan Normal
Course: Organic Chemistry
Keywords: Allenic ketones Pyrazole derivatives Copper-catalyzed couplings Tandem reactions 5-(Isoxazol-3-yl) pyrimidine nucleosides
CLC: O621.3
Type: Master's thesis
Year: 2013
Downloads: 52
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Abstract


In this thesis, a wide range of pyrazole derivatives and5-(isoxazol-3-yl) pyrimidine nucleosides weredesigned and synthesized. It mainly includes the following four parts:First, we have developed a facile methodology for the synthesis of3,5-disubstituted pyrazolederivatives through the cyclocondensation reaction of allenic ketones and hydrazines. By using this method,5-(5-methyl-pyrazol-3-yl)-2’-deoxycytidine was successfully prepared with good efficiency. Advantages ofthis method include easily obtainable starting materials, free of expensive catalysts, and extremely mildreaction conditions.Then, a highly regioselective protocol for the synthesis of1-acyl-5-hydroxypyrazolines throughcyclocondensation of allenic ketones with hydrazides in the absence of any catalysts has been developed.The thus formed1-acyl-5-hydroxypyrazolines can be further converted into1-acyl pyrazoles viaBF3·Et2O-catalyzed dehydration. In addition,1-acyl pyrazoles can also be obtained directly from allenicketones and hydrazides through a one-pot procedure.Next, we have developed a facile methodology for the synthesis of pyrazolo[1,5-c]quinazolines or5,6-dihydropyrazolo[1,5-c]quinazolines through copper-catalyzed tandem reaction of5-(2-bromoaryl)-1H-pyrazoles with aqueous ammonia and carbonyl compounds under air atmosphere.Interestingly, with cyclic ketones, the corresponding spiro-5,6-dihydropyrazolo[1,5-c]quinazolines weresuccessfully synthesized in modest yields. Moreover, we found that the tandem reaction could also becarried out in a one-pot, four-component manner by starting with1-(2-bromophenyl)-1,3-diones, hydrazinehydrate, carbonyl compounds, and aqueous ammonia.At last, a highly efficient method for the preparation of5-(isoxazol-3-yl) pyrimidine nucleosides viathe1,3-dipolar cycloaddition of5-chloroaldoxime substituted pyrimidine nucleosides with terminal alkynesunder the promotion of triethylamine has also been developed. Compared to the known methods towardC5-(isoxazol-3-yl) pyrimidine nucleosides, the remarkable advantage of this procedure is free of expensivecatalysts.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Synthetic organic chemistry
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