Microwave-Assisted Synthesis of Sulfur and Nitrogen-Containing Heterocycles

Benzo[1,5]thiazepine: Synthesis, Reactions, Spectroscopy, and Applications

“…To enhance the anxiolytic activity of some azepine derivatives by the introduction of a trifluoromethyl group in the dia-, oxa-or thiazepine, trifluoroacetyl ketene acetals 167 were reacted with o-aminothiophenol derivatives in the presence of xylene, applying a multimode microwave oven (8-12 min at 980 W). Although this methodology uses microwave inert solvents (e.g., toluene or xylene), which are not serving in the energy transfer processes, it gave the 3-substituted 2-hydroxy-2-trifluoromethyl-1,5-benzothiaz-epine derivatives 168 in good yields, suggesting absorption of the microwaves by the reactants [33,35,36,39] …”

Review of Microwave-Assisted Synthesis of Benzo-Fused Six-MemberedN,N-Heterocycles

“…Liu and co-workers [91] disclosed an elegant microwave-assisted domino process for the total synthesis of quinazolinobenzodiazepine alkaloids such as sclerotigenin, circumdatin F and asperlicin C. The methodology involves treatment of anthranilic acid with the corresponding N-Boc protected amino acids in the presence of P(OPh) 3 in pyridine at 230 o C for 20 min. The developed one-pot approach is noteworthy as it utilizes a single reagent (P(OPh) 3 ) and protecting group in the total synthesis from readily available precursors. Reaction mixtures requiring only anthranilic acid/derivatives, various NH-Boc protected amino acids, triphenyl phosphine and pyridine generated a range of natural products.…”

“…[91][92] Isaindigotone was prepared [93] in a two stage MW-assisted one-pot reaction. Anthranilic acid, 4-(tert-butoxycarbonylamino)butyric acid with P(OPh) 3 The pyrroloquinazolinoquinoline alkaloids Luotonin A and B were isolated recently from the aerial parts of Peganum nigellastrum, a plant that has been used against rheumatism, abscesses and inflammation in Chinese traditional medicine. The alkaloid Luotonin A was found to possess a pentacyclic skeleton closely resembling Camptothecin, derivatives of which are clinically useful anticancer agents.…”

Role of Microwaves in the Synthesis of Fused Five-Membered Heterocycles with Three N-Heteroatoms

“…[3,4] In many cases, the classic syntheses provide reliable access to heterocyclic compounds, however, they are simply no longer acceptable by current environmental and safety standards. For all these reasons, the various possibilities offered by the microwave technology are particularly attractive where fast, high-yielding protocols and the avoidance or facilitation of purification are highly desirable.…”