Methenamine (L18), a commercially available and inexpensive material, was found to be efficient in the Ullmann etherification by Qian’s team. This methodology was applicable to a variety of phenols and aryl halides under mild conditions; twenty-eight compounds were obtained in moderate to excellent yields, except for p-acylphenol (, Entry 7). Notably, methenamine, a low molecular weight polymer of ammonia and formaldehyde, is also an antibiotic and undergoes acidic hydrolysis to give the active component formaldehyde with antimicrobial property.
Bunker et al, prepared a series of 1, 2-benzothiazine derivatives.They claimed that these compounds were useful in treating the elevated blood pressure and hypertension as endothelin antagonists 29.
solvent-free green synthesis of 1,4-benzothiazine by the coupling ..
In 2011, Balalaie et al. developed a practical protocol for the synthesis of indolo[1,2-α]quinoxalinones via a sequential 4-component Ugi reaction and subsequent Ullmann intramolecular N-arylation catalyzed by the CuI/L-proline (L19) system ().
Microwave assisted synthesis of 1,4-benzothiazine esters
Chloroquine (CQ), one of the quinine drug class, has been widely used for antimalarial therapy., However, due to the emergence of CQ-resistant strains of P. falciparum, the most lethal form of malaria, there is an urgent need to develop new quinine drugs with improved antimalarial activity and low cross-resistance profile. Recently, a chemical library of 7-substituted 4-aminoquinoline was synthesized by Guy’s groupvia Ullmann, Suzuki, and Negishi coupling strategies. All the compounds were tested against CQ-sensitive (3D7) and -resistant (K1) strains of P. falciparum, as well as four mammalian cell lines (HepG2, HEK293, Raji, and BJ) in concentration-response experiments (). Biological data demonstrated that less lipophilic compounds performed higher bioactivities, especially for the biaryl series.
Microwave induced Synthesis of 1,4-benzothiazine bearing ..
A small chemical library of diarylheptanoid engelhardione and derivatives bearing the oxime, N- and O-alkylated functionalities were designed and synthesized by Sun and coworkers. Antibacterial evaluation revealed that the reductive amination derivatives A and B showed moderate activities with minimum inhibitory concentrations (MIC) values of 12.5–25 μg/mL against Mycobacterium tuberculosis and Gram-positive pathogens, as well as anti-Gram-negative activity against an efflux impaired E. coli strain ().
reactions and biological activity of 1,4-benzothiazine derivatives ..
In 2012, Luo et al. reported the synthesis and evaluation of a series of diaryl ethers as potential antitubercular agents (, Left). The same year, several xanthone derivatives as nerve conduction blockers (, Right) were prepared by Pinto et al.via Ullmann and Friedel-Craft reactions.
Synthesis and pharmacological evaluation of 4H-1,4-benzothiazine …
The Ullmann O-arylation is extensively employed in the synthesis of drug-like molecules. In 2012, three ether derivatives containing a thieno[3,2-b]pyridyl ring system were prepared by Queiroz et al.via the Ullmann O-arylation (). The anti-cancer inhibitory activities of these compounds against a panel of human tumor cell lines including MCF-7 (breast adenocarcinoma), A375-C5 (melanoma), and NCI-H460 (non-small cell lung cancer) were biologically evaluated; such evaluation revealed that the ether derivatives with o- and m-MeO group showed promising anti-cancer activity.