The Synthesis Of Pyrazoline Derivatives Mediated By Dialkyl Azodicarboxylate

Pyrazoline derivatives is a kind of five-membered nitrogen heterocycles with high biological activities and diverse structures. They widely exist in the natural products and synthetic drug molecules and are considered to be very important in the application and development of pharmaceutical, organic synthesis, biological chemistry and materials science. To find convenient, efficient and green methods for the synthesis of pyrazoline derivatives is the focus of numerous scientists. Dialkyl azodicarboxylate, as an efficient oxidation and amination reagent, is an important coupling reagent for the formation of SP3C-C, C-N, C-O, C-S bonds.The contents of this essay as follows:1. Use of Dialkyl azodicarboxylate and1,3-substituted propyne compounds as the starting materials, a simple, efficient and green methods for the synthesis of1,3-substituted propargyl hydrazine derivatives is established. Several reaction conditions were tried and a tentative mechanism was presented. Typical reaction is as follows:The reaction was carried out in the yield of81%with1eq1,3-diphenyl allylene and2.5eq diethyl azodicarboxylate as materials,5%K2CO3, N2protection and solvent free under40℃, and the corresponding product is N,N’-dicarbethoxy-N-(1,3-diphenyl propargyl) hydrazine. 2. Catalyzed by palladium acetate, the synthesis of3-pyrazoline derivatives was realized by the intramolecular cyclization of above-obtained1,3-substituted propargyl hydrazine derivatives. Most of the1,3-substituted propargyl hydrazine derivatives can be transformed to corresponding3-pyrazoline derivatives, which is a new route for the synthesis of3-pyrazoline derivatives. Typical reaction is as follows:The reaction was carried out in the yield of76%with N,N’-dicarbethoxy-N-(1,3-diphenyl propargyl) hydrazine as material,5%Pd(AcO)2and N2protection in toluene under rt, and the corresponding product is1,2-dicarbethoxy-3,5-diphenyl-3-pyrazoline.