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Abstract
Polyfunctional building blocks are essential for the implementation of diversity-oriented synthetic strategies, highly demanded in small molecule libraries’ design for modern drug discovery. Acyl(imidoyl)ketenes are highly reactive organic compounds, bearing both oxa- and aza-diene moieties, conjugated symmetrically to the ketene fragment, enabling synthesis of various skeletally diverse heterocycles on their basis. The highlights of reactions utilizing acyl(imidoyl)ketenes are high yields, short reaction time (about several minutes), high selectivity, atom economy, and simple purification procedures, which benefits the drug discovery. The present review focuses on the approaches to thermal generation of acyl(imidoyl)ketenes, patterns of their immediate transformations via intra- and intermolecular reactions, including the reactions of cyclodimerization, in which either symmetric or dissymmetric heterocycles can be formed. Recent advances in investigations on mechanisms, identifications of intermediates, and chemo- and regioselectivity of reactions with participation of acyl(imidoyl)ketenes are also covered.
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Abstract
Pyrazolo-oxazine fused systems are interesting classes of heterocyclic compounds
exhibiting pronounced biological applications such as anticancer, antitubercular,
anti-inflammatory, antibacterial and antifungal activities as well as inhibiting COX-1 and
COX-2 enzymes. Depending on the distribution position of the heteroatoms (N and O), there
are fourteen different systems of pyrazolo-oxazine. Nine of them were biologically abundant
in literature, for example, pyrazolo[3,4-e][1,3]oxazines are used as analogs of antibiotics
Formycin, Formycin B, Oxoformycin B. This review article summarizes the concerted efforts
expended on most of the synthetic routes to the various types of pyrazolo-oxazines in
the literature until the first quarter of 2020. The reactions of pyrazolo-oxazines with various
reagents are also outlined.
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Affiliation(s)
- Kamal M. Dawood
- Department of Chemistry, Faculty of Science, Cairo University, Giza, 12613, Egypt
| | - Thoraya A. Farghaly
- Department of Chemistry, Faculty of Science, Cairo University, Giza, 12613, Egypt
| | - Mohamed A. Raslan
- Department of Chemistry, Faculty of Science, Aswan University, 81528 Aswan, Egypt
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Zhulanov VE, Vigovskaya VA, Dmitriev MV, Silaichev PS, Maslivets AN, Rubin M. Dipyrazolodioxadiazocines as shelf-stable "ready-to-use" precursors for an in situ generation of enolate-iminium 1,4-dipoles: a straightforward atom-economical approach to pyrazolo[5,1-d][1,3,5]dioxazines. Org Biomol Chem 2020; 18:3382-3391. [PMID: 32323682 DOI: 10.1039/d0ob00451k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An original, facile and highly efficient method for the in situ generation of cyclic enolate-iminium 1,4-dipoles via unique thermal decomposition of easily available dipyrazolodioxadiazocines has been developed. Various substituted pyrazolo[5,1-d][1,3,5]dioxazines have been prepared in high yields via unusual cycloconversion of dipyrazolodioxadiazocines in the presence of ketones. Furthermore, the developed method is 100% atom economical and proceeds under metal-, catalyst- and solvent-free conditions.
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Affiliation(s)
- Vladimir E Zhulanov
- Department of Chemistry, Perm State University, ul. Bukireva 15, Perm, 614990, Russian Federation.
| | - Valeria A Vigovskaya
- Department of Chemistry, Perm State University, ul. Bukireva 15, Perm, 614990, Russian Federation.
| | - Maksim V Dmitriev
- Department of Chemistry, Perm State University, ul. Bukireva 15, Perm, 614990, Russian Federation.
| | - Pavel S Silaichev
- Department of Chemistry, Perm State University, ul. Bukireva 15, Perm, 614990, Russian Federation.
| | - Andrey N Maslivets
- Department of Chemistry, Perm State University, ul. Bukireva 15, Perm, 614990, Russian Federation.
| | - Michael Rubin
- Department of Chemistry, North Caucasus Federal University, 1a Pushkin St., Stavropol 355009, Russian Federation and Department of Chemistry, University of Kansas, 1567 Irving Hill Rd., Lawrence, KS 66045-7582, USA.
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