Abstract
1H-quninoxalin-2-one is a fused, aromatic heterocycle whose derivatives have exhibited interesting biological activities, including antibiotic, antifungal, and antituberculosis properties. Investigations into the synthesis of this molecule may aid in the targeted design of new derivatives. The synthesis of 1H-quninoxalin-2-one through the E1CB elimination of an alkylated quinoxalinone was investigated in order to gain an understanding of the overall reaction mechanism and what factors influence the product composition. Various conditions such as solvent, temperature, and base were studied in connection with optimization of a new, one-pot microwave synthesis of 1H-quninoxalin-2-one. The ultimate goal was to determine the mechanism by which the product forms in a one pot synthesis. While the new, Microwave-assisted Organic Synthesis (MAOS) approach was successful in optimizing product yield, the mechanism is still unknown.
Benzimidazole is another fused, aromatic heterocycle which is a biologically important scaffold and is a useful structural motif for the development of molecules of pharmaceutical or biological interest. It is proposed that the greenest mechanistic route to synthesize benzimidazole is via the condensation of o-phenylenediamine with formic acid solution using a new, Microwave-assisted organic synthesis approach. In this study different conditions such as solvent, temperature, and various functional groups were studied in order to optimize this reaction under microwave heating. Activating (alkyl and methoxy) and deactivating (chloro and nitro) groups were studied, and it was found that deactivating groups favor the condensation reaction more, producing benzimidazole derivatives in high yields and purities.
Benzodiazepines are fused, aromatic heterocycles which have exhibited interesting anxiolytic, antitumor, and anticonvulsant properties. The synthesis of these seven-membered ring structures is notoriously difficult but was successfully accomplished through a condensation reaction between o-phenylenediamine and malonic acid using a Microwave-assisted organic synthesis approach. This reaction was optimized by studying the effect of catalyst, solvent, temperature, and various functional groups on the yield and purity of the product formation. It was found that mildly activating and deactivating groups lead to the formation of 1,5-benzodiazepine-2,4-dione derivatives in good yields, while strongly deactivating or sterically hindered groups prevented the formation of the desired product.