Investigation On Methodology For The Synthesis Of Nitrogen Heterocycles

Nitrogenous heterocyclic compounds play an important role inheterocyclic compounds, many chemists are enthusiastic about researchingthem due to their unique biological activity.1,4-Dihydropyridines are a kindof important calcium channel blockers and widely used in the treatment ofhypertension, angina pectoris, arrhythmia and other cardiovascular diseases.Nitrogenous four-membered ring compounds have special antibacterialactivity and play an important role in many conversion reaction due to theirspecial constrained structure. In addition, they also can be used as theintermediates to synthetize many amino acids, alkaloids and other natural orunnatural biological macromolecular compounds. Therefore, it is significantto study the novel synthetic methods of1,4-Dihydropyridines and nitrogenousfour-membered ring compounds. In this dissertation, our work is aboutdeveloping novel synthethic methodologies, which can be specialized as thefollowing:1. One-pot synthesis of4-aryl-N-OH-Hantzsch estersA mild and convenient one-pot method for the synthesis ofN-OH-Hantzsch esters was developed. The key step is controlling the firstMichael addition at relatively lower temperature (0oC) to prevent the furthercyclization. To optimize the addition reactions for better yield, varioussolvents and bases were screened. Symmetrical and unsymmetricalN-OH-Hantzsch esters can be easily obtained in moderate yield using thismethodology. Furthermore, the terminal hydroxyl group makesN-OH-Hantzsch esters be further transformed or introduced to other moleculeeasily for further investigation of the potential use in medicinal fields. Themethodology is considered to be simple, gentle and with low cost.2. Study on the stereoselective synthesis of1,3-diazabicyclo heptanesand heptenes in the presence of iodineWe studied the one-pot preparation of1,3-diazabicyclo heptanes andheptenes with high stereoselectivities from substituted amino diethylmalonates and chalcones mediated by I2and base. The influence of the base,solvent and reaction temperature on those reactions was investigated in detail. We also explored an efficient method to construct imidazolidine derivativeswith high yield and diastereoselectivity. Moreover, we studied investigatedthe ring-opening reaction of1,3-diazabicyclo heptanes with differentnucleophilic reagents. The advantages such as being mild and simple, lowcost, the high chemoselectivity and wide range of applications make thecurrent method very attractive and appealing.