We conducted a comparative study on the development of two synthetic methods. The solvent-free synthesis is a green chemistry method developed in a bid to ameliorate environmental adverse effects of the conventional solvent-based synthesis. The synthesis of novel dichloro and polymethoxy p-nitrophenylhydrazones through solvent free technique gave moderate to high yields which were however lower than those of the solvent-based method. The established solvent-free approach has several benefits, including universality and simplicity of the approach, catalyst-free conditions, non-use of an organic solvent, quick reaction time, fast and efficient workup, and un-solvated pure products in moderate to high yields.

As a result of this work, a previously unreported benzoxazine monomer based on 3,3'-dichloro-4,4'-diaminodiphenylmethane was obtained, characterized by 1H and 13C NMR spectroscopy, and its thermal and rheological properties were studied. A comparison between the properties of benzoxazines based on diamines (3,3'-dichloro-4,4'-diaminodiphenylmethane and 4,4’-diaminodimethylmethane). The effect of the reaction medium on the structure of the oligomeric fraction and the overall yield of the main product was studied. The synthesized monomers can be used as thermo- and fire-resistant binders for polymer composite materials, as well as hardeners for epoxy resins.

(R)-1-(4-Amino-3,5-dichlorophenyl)-2-bromoethan-1-ol has been synthesised in 93% enantiomeric excess (ee) by asymmetric reduction of the corresponding ketone catalysed by a ketoreductase and NADPH as the co-factor in DMSO. (S)-N-(2,6-Dichloro-4-(1-hydroxyethyl)phenyl)acetamide has been synthesised in >98% ee by the same system. Both synthons are potential precursors for clenbuterol enantiomers. Clenbuterol is a β₂-agonist used in veterinary treatment of asthma in several countries. The drug is listed on the World Anti-doping Agency’s Prohibited list due to its effect on increased protein synthesis in the body. However, racemic clenbuterol has recently been shown to reduce the risk of Parkinson’s disease. In order to reveal which one (or both) of the enantiomers that cause this effect, the pure enantiomers need to be studied separately. Our biocatalytic approach in order to obtain enantiopure clenbuterol should be applicable to industrial scale.