The Cadogan reaction, a widely accepted route for the synthesis of nitrogen containing heterocycles, is modified by using microwave radiation as the source of heat instead of the conventional heating by reflux in a nitrogen atmosphere for several hours. Appropriate starting materials were mixed with triethyl phosphite or triphenylphosphine and irradiated with microwaves for several minutes at a specific power to give the desired products. The indazoles were prepared by irradiating N‐(2‐nitrobenzylidene) anilines with triethyl phosphite at 200 W for 12–14 min to give 85–92% product yields. Irradiation of the mixture of N‐benzylidene‐2‐nitroanilines and triphenylphosphine at 200 W for 3–5 min yielded 93–96% of the benzimidazoles. The carbonylindoles were obtained in 61–68% yields by irradiating 2‐nitrochalcone or alkyl 2‐nitrocinnamates and triphenylphosphine with microwaves at 80–200 W for 8–11 min. The mixture of 2‐nitrobiphenyl and triphenylphosphine yielded 96% of carbazole when irradiated with microwaves at 200 W for 2 min while 75% of phenazine was obtained by irradiating the mixture of 2‐nitrodiphenylamine and triphenylphosphine with microwaves at 200 W for 3.5 min. These results show that microwave‐assisted Cadogan reactions gave better product yields at shorter reaction times. J. Heterocyclic Chem., (2009).

Aim: The prevailing crisis caused by the COVID-19 pandemic demands the development of effective therapeutic agents that can be implemented with minimal to zero adverse effects. Background: Vitex negundo L. (VNL) is a medicinal plant with reported efficacy against respiratory diseases and some of the COVID-19 symptoms. Funded by the Department of Science and Technology (DOST), the University of the Philippines – Philippine General Hospital (UP-PGH) is currently conducting clinical trials of VNL and other medicinal plants as adjuvant therapeutic agents against mild cases of COVID-19. The basis for the clinical trials is primarily the pharmacological efficacy of the medicinal plants against respiratory disorders and associated COVID-19 symptoms. Objective: This study assessed the in silico potential of VNL components against SARS-CoV-2 main protease (Mpro), an enzyme that plays an important role in COVID-19, the disease caused by the SARS-CoV-2. Objective: This study assessed the in silico potential of VNL components against SARS-CoV-2 main protease (Mpro), an enzyme that plays an important role in COVID-19, the disease caused by the SARS-CoV-2. Method: Phytochemical mining of VNL components from the literature was conducted. A database consisting of 250 known compounds from different parts of VNL was created and screened against SARS-CoV-2 Mpro using the PyRx virtual screening tool. The most promising components were further subjected to in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) analyses using the SwissADME web server and Toxtree software. Results: Virtual screening revealed that 102 VNL components in the database had comparable to or better binding affinities toward SARS-COV-2 Mpro than known chemical inhibitors (e.g. N3 and carmofur). It was determined that the active site of SARS-CoV-2 Mpro receptor consists of multiple H-donor and acceptor sites; hence, the most stable receptor-ligand complexes are generally formed by VNL ligands that establish effective H-bonding with the SARS-CoV-2 Mpro. The promising components, representing a “cocktail” of potential inhibitors also revealed interesting ADMET properties. Conclusion: This in silico study identified VNL as a potential single source of a cocktail of SARS-CoV-2 Mpro inhibitors and a promising adjuvant therapeutic agent against COVID-19 or its symptoms. Furthermore, the study offers a rationale on phytochemical mining from medicinal plants as a means that can be implemented in the early stage of a drug discovery and development program.

The Fischer indole synthesis was carried out using microwaves instead of conventional heating procedures. When the mixture of phenylhydrazine, cyclohexanone and zinc chloride was irradiated at 600 W for 3 min, 76% of 1,2,3,4‐tetrahydrocarbazole was obtained. However, when zinc chloride was replaced with p‐toluenesulfonic acid (p‐TSA), the reaction yielded 91% of 1,2,3,4‐tetrahydrocarbazole. Thus, a series of indoles were prepared using microwaves in the presence of p‐TSA catalyst. J. Heterocyclic Chem., (2011).

A variety of nitrogen-containing heterocycles were synthesized by passing vapors of aromatic amines over calcium oxide at 450-650 °C under nitrogen carrier gas. Reaction of 2-aminobiphenyl 3 a at 560 °C gave carbazole 4 in 80% yield. Reaction of 2,2'-diaminobiphenyl 3 b a fforded a mixture of carbazole 4 a n d 4-aminocarbozole 6 b. In the case of 2-amino-2'-nitrobiphenyl 3 c, benzo[c]cinnoline 7 was obtained along with carbazole 4. Reaction of 2-amino-2'-methoxybiphenyl 3 d gave four products of carbazole 4, 4-hydroxycarbazole 6 e, phenanthridine 8 and dibenzofuran 9. Reaction of 2-aminodiphenylmethane 5 a a fforded acridine 1 0. In the case of 2-aminobenzophenone 5 b, acridone 11 was obtained as a major product. Reaction of 2-aminobenzhydrol 5 c gave acridine 1 0. When 2-aminodiphenylamine 5 d was reacted, phenazine 1 2 w a s obtained in good yield. In contrast, reaction of 2-aminodiphenyl ether 5 e produced only 2-hydroxydiphenylamine 1 3. Reaction of 4-aminophenanthrene 1 4 produced 4H-b e n z o [d e f]carbazole 1 5 in 61% yield.