A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series. Keywords: [3 + 2]-cycloadditions; fluorinated compounds; fused pyrazoles; N-heterocycles; nitrile imines; 1,4-quinones; Introduction The 1,4-quinone scaffold belongs to the most important

• reported in the 1960s [17]. The latter 1,3-dipole was generated thermally from the respective tetrazole derivative 3, and the observed [3 + 2]-cycloadditions occurred chemoselectively to provide fused pyrazoles of the type 4 as exclusive products (Scheme 1). This type of cycloaddition attracted

• ]-cycloadducts by air oxidation were isolated exclusively. Additionally, the X-ray structure of 9d is shown in Figure 2. Similar results were obtained starting with 1,4-anthraquinone (1b) and selected hydrazonoyl bromides 8. In this series, fused pyrazoles 9i–l were obtained in high yield (63–92%, Scheme 3

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

• resemblance. In addition to the immense biological potential related to fused pyrazoles, their synthetic potential needs to be reviewed for further improvements and extension of interests. Various efforts have been developed for the synthesis of pyrazole-based fused heterocycles. 5-Aminopyrazoles have been

Use of activated enol ethers in the synthesis of pyrazoles: reactions with hydrazine and a study of pyrazole tautomerism

• Denisa Tarabová,
• Stanislava Šoralová,
• Martin Breza,
• Marek Fronc,
• Wolfgang Holzer and
• Viktor Milata

Beilstein J. Org. Chem. 2014, 10, 752–760, doi:10.3762/bjoc.10.70

• ), 1,3-dipolar cycloaddition with diazo compounds as a source of N–N linkage, degradation of fused pyrazoles or rearrangement of other monocyclic heterocycles under chemical, thermal or photochemical conditions [4]. Upon reaction of hydrazine with symmetrical enol ethers, only a single product is formed

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

• corresponding tricyclic naphthalene fused pyrazoles 15 (Scheme 12, path A). Moreover, in a subsequent work, the authors applied the same strategy to obtain pyrazolo[4,3-b]indoles 16, a new class of CK2 inhibitors [42]. These products were obtained starting from properly substituted dihydropyrazoles 13 in which

Dipyrazolo[1,5-a:4',3'-c]pyridines – a new heterocyclic system accessed via multicomponent reaction

• Wolfgang Holzer,
• Gytė Vilkauskaitė,
• Eglė Arbačiauskienė and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2012, 8, 2223–2229, doi:10.3762/bjoc.8.251

• of adenosine and, thus, has been incorporated in various compounds impairing protein kinases and ATPases [7][8][9]. Moreover, a large variety of additional fused pyrazoles exhibit interesting biological activities, such as, pyrazolo[1,5-a]quinolones [10], pyrazolo[4,3-c]quinolones [11], pyrazolo[5,1