Research On New Synthetic Methods Of N,N’-diacylhydrazines,1,3,4-oxadiazoles,1,5-diketones And Chloroacetals

Complex operation,low yield,high cost and high pollution are important obstacles for practical applications of organic synthetic methods.This dissertation is aimed at solving the problems by developing new methods for the synthesis of N,N’-diacylhydrazines,1,3,4-oxadiazoles,1,5-diketones andα-chloroacetals.Firstly,39 N,N’-diacylhydrazines were synthesized from aldehyde hydrazones and N,N-dimethylamides in the presence of CuBr₂ in air and the yield was up to 97%.Thenseventeen1,3,4-oxadiazolesincludingfourteen2,5-disubstituted1,3,4-oxadiazoles and three 2-substituted 1,3,4-oxadiazoles were obtained with the highest yield of 91%using N-t-butyl aldehyde hydrazones and N,N-dimethylamides as starting materials.In the synthesis of N,N’-diacylhydrazines and1,3,4-oxadiazoles,N,N-dimethylamides was used as the acylation reagent for the first time.Especially when DMF was used as the formylation reagent it was also used as the solvent which simplified the reaction operation.The reaction cost was reduced to a great extent by using inexpensive and low-toxicity copper（II）bromide as promoter and using air as oxidant and source of oxygen atoms.These reactions have other advantages such as short reaction times,tolerance of a broad scope of functional groups,simple workup,and high yields.Secondly,24 anti-1,5-diketones was stereospecifically synthesized from methyl aromatic ketones and aliphatic aldehydes in the presence of TBAB or Aliquat 336,KOH in water.And the yield was up to 96%.That the water was used as reaction medium not only improved the reaction yield,simplified the operation,lowered the cost and reduced the environmental pollution,but also showed great advantage in stereoselectivity.Besides,these reactions have the following advantages:tolerance of a broad scope of functional groups,simple workup,easiness to scale up,recyclability of phase transfer catalyst（PTC）and aqueous media.This result compares favorably to the literature methods（around 69%yield,anti:syn=6.7:1 in the literature vs 96%yield,sole anti isomers in this work）.Lastly,16α-chloroacetals were synthesized from primary alcohols in the presence of TEMPO and TCCA under solvent-free conditions.And the yield was up to 90%.Althoughα-chloroacetals are important intermediates,in organic solvents primary alcohols could not be transferred intoα-chloroacetals directly in the presence of TEMPO and TCCA.This goal was achieved under solvent-free conditions which simplified the operation and reduced the use of organic solvents.And that inexpensive TCCA was used as oxidant and chlorinated reagent also saved the reaction cost.