Study On The Reduction Of Aldehydes And Ketones With Ammonia-borane And Synthesis Of N,N'-di-sec-butyl-p-phenylenediamine

In the past three years, ammonia borane (NH3BH3, AB) and some derivatives ofAB have been widely utilized in synthetic organic chemistry. Compared withtraditional reductants, AB and its derivatives are more wild reagents, own specificselectivity on C=O groups. AB and M(NH2BH3)Xhave been reported as reductants. Inthis study, Co-doped AB and MeAB have been applied on chemoselective reductionof carbonyl compounds.1. A “co-precipitation” method was applied to introduce nanosized Co-basedcatalysts to AB. It was observed that Co-doped AB exhibited much betterperformance than AB in chemoselective reduction of several aldehydes and ketones. Itis noteworthy that aromatic ketones could be reduced by Co-doped AB with highyields at room temperature within several hours. EPR characterization revealed thatCo element in a partially reduced state.2. MeAB was synthesized by CH3NH2HCland NaBH4in THF. The reaction route of reduction of carbonyl compounds withMeAB in neat water was discussed. Aldehydes were selective reduced rapidly inquantitative conversions and excellent yields. But reduction of aromatic ketonesneeded over20h at rt due to their poor water-solubility and steric hindrance. Thus weinvestigated PEG400as phase-transfer catalyst (PTC) and acidic cation-exchangeresin D072as acid catalysts to accelerate the redcution of aromatic ketones, andachieved excellent yields within several hours. D072resin could be reused up tofour times without any significance loss in activity.N,N'-di-sec-butyl p-phenylenediamine (DBPD) was an important class of organicintermediates and products, which are widely applied in fine chemical,pharmaceuticals, agricultural chemicals, pigments, rubber antioxidants and antiseptics.Among the synthetic methods for N,N'-di-alkyl-p-phenylene diamines, the reductivealkylation of p-nitroaniline with ketone is of most applied value. In this study, DBPDwas prepared from p-nitroaniline and butanone catalyzed by Cu-Cr-La/?-Al2O3catalysts in autoclave.1. A series of Cu-based catalysts were designed, prepared and examined for thisreductive alkylation, thereinto, CuCrLa/?-Al2O3showed excellent results and waschosen for this reaction. The catalysts were studied by TEM and SEM. It was foundthat doped Cr remarkably enhanced the activity and stability of Cu/?-Al2O3due to the better dispersion of Cu0which can supply more active centers and prevent thesintering and aggregation of copper. Additionally, it was found that the introduction ofLa to CuCr/?-Al2O3led to a higher selectivity because of a remarkable decrease of thecatalyst acidity.2. The effects of such factors as the selection of catalyst, reactiontemperature, reaction time, reaction pressure and the ratio of the reactants on thereaction were investigated. The best reaction condition of synthesis of DBPD was asfollows: reaction temperature was180?, reaction time was10h, reaction pressurewas3.5MPa, the mass ratio of p-nitroaniline and butanone was1:4. The bestreaction condition resulted in the target product in97.0%purity and the conversionof p-nitroaniline was100%. The catalysts could be reused to four times without anysignificant loss in activity. On the basis of experiment in the laboratory, pilotexperiment was carried out successfully.