4454-31-3Relevant academic research and scientific papers
The tautomerism of indazolinone in aqueous solution. A note on the 'principle of vinylogy'
Bruneau, Pierre,Taylor, Peter J.,Wilkinson, Anthony J.
, p. 2263 - 2269 (1996)
Correction factors derived in another study have been applied to the basic pKa values of fixed model tautomers in order to elucidate the tautomeric balance for indazolinone 1 in aqueous solution. The oxo-form B dominates to the extent of ca. 95%; this is consistent with past studies in other solvents. Of the two possible hydroxy tautomers, the benzenoid form A accounts for almost all of the remainder, the proportion of the quinonoid form C being estimated as ca. 10-4.7. It has also proved possible to estimate all six of the microscopic acid pKas values; as with the basic pKas, the resultant of these agrees very closely with the measured, macroscopic pKa, of 1 itself. 1-Substitution engenders a switch to tautomer A; AM1 calculations suggest that the reason may be enforced planarity, leading to a severe (R)N-NH lone pair clash in B which destabilises this form. Comparison with N-unsubstituted pyrazolones shows that benzene ring annelation has the expected effect of stabilising B and destabilising C. However, it is noted that A is more stable than C even when no quinonoid form is possible, and that this reflects a greater basicity for heterocycles in general when substituted with π-donors γ- rather than α- to aza-nitrogen. It is suggested that this effect applies equally in other contexts, as when C=O not C=N is the π-acceptor; that its origin lies in a-bond-no-bond resonance which acts specifically to limit conjugation when π-donor and π-acceptor are contiguous; and that this phenomenon throws much light on the 'principle of vinylogy'.
Rhodium(III)-catalyzed N-nitroso-directed C-H addition to ethyl 2-oxoacetate for cycloaddition/fragmentation synthesis of indazoles
Chen, Jinsen,Chen, Pei,Song, Chao,Zhu, Jin
, p. 14245 - 14249 (2015/02/05)
RhIII-catalyzed N-nitroso-directed C-H addition to ethyl 2-oxoacetate allows subsequent construction of indazoles, a privileged heterocycle scaffold in synthetic chemistry, through the exploitation of reactivity between the directing group and installed group. The formal [2+2] cycloaddition/fragmentation reaction pathway identified herein, a unique reactivity pattern hitherto elusive for the N-nitroso group, emphasizes the importance of forward reactivity analysis in the development of useful C-H functionalization-based synthetic tools. The synthetic utility of the protocol is demonstrated with the synthesis of a tri-cyclic-fused ring system. The diversity of covalent linkages available for the nitroso group should enable the extension of the genre of reactivity reported herein to the synthesis of other types of heterocycles.
Synthesis, biological evaluation and chemometric analysis of indazole derivatives. 1,2-Disubstituted 5-nitroindazolinones, new prototypes of antichagasic drug
Vega, María Celeste,Rolón, Miriam,Montero-Torres, Alina,Fonseca-Berzal, Cristina,Escario, José Antonio,Gómez-Barrio, Alicia,Gálvez, Jorge,Marrero-Ponce, Yovani,Arán, Vicente J.
, p. 214 - 227 (2013/02/23)
Chagas disease chemotherapy, currently based on only two drugs, nifurtimox and benznidazole, is far from satisfactory and therefore the development of new antichagasic compounds remains an important goal. On the basis of antichagasic properties previously
The Heterocyclization of N',N'-Disubstituted 2-Halogenobenzohydrazides to 1,1-Disubstituted Indazol-3-ylio Oxides
Aran, Vicente J.,Asensio, Juan L.,Ruiz, Jose R.,Stud, Manfred
, p. 1322 - 1345 (2007/10/02)
The intramolecular cyclization of N',N'-disubstituted 2-halogenobenzohydrazides is a good method for the synthesis of the previously unknown indazol-3-ylio oxides.The Z/E rotamerism found in the starting hydrazides, the effects of the nature and the activ
