ChemInform Abstract: NITRILE CYCLIZATION REACTIONS. VI. SYNTHESIS OF 2‐AMINO‐4‐(2‐FURYL)‐4H‐PYRANS

Sharanin, Yu. A.; Shcherbina, L. N.; Sharanina, L. G.; Puzanova, V. V.

doi:10.1002/chin.198324233

Cited by 21 publications

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“…1g Due to their biological significance,1 there has been considerable interest in developing synthetic methods for 6-amino-5-cyanodihydro-pyrano[ 2,3- c ]pyrazoles 2–6. These compounds may be readily obtained from the reaction of 4-arylmethylene-5-pyrazolone and malononitrile, 2,3 or 2-pyrazolin-5-ones and benzylidenemalononitriles 3. The overall reaction is a tandem Michael addition and a Thorpe-Ziegler type reaction (an enol addition to a cyano group) followed by tautomerization 3.…”

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confidence: 99%

Organocatalyzed enantioselective synthesis of 6-amino-5-cyanodihydropyrano[2,3-c]pyrazoles

Gogoi

Zhao

2009

Tetrahedron Letters

178

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The first enantioselective synthesis of biologically active 6-amino-5-cyanodihydropyrano [2,3-c] pyrazoles has been achieved through a cinchona alkaloid-catalyzed tandem Michael addition and Thorpe-Ziegler type reaction between 2-pyrazolin-5-ones and benzylidenemalononitriles. The reaction may also be carried out in a three-component or a four-component fashion via the in situ formation of these two components from simple and readily available starting materials. The desired products were obtained in excellent yields with mediocre to excellent enantioselectivities (up to >99% ee). KeywordsDihydropyrano [2, 3-c] (Fig. 1). 1g Due to their biological significance, 1 there has been considerable interest in developing synthetic methods for 6-amino-5-cyanodihydro-pyrano [ 2,3-c]pyrazoles. [2][3][4][5][6] These compounds may be readily obtained from the reaction of 4-arylmethylene-5-pyrazolone and malononitrile, 2,3 or 2-pyrazolin-5-ones and benzylidenemalononitriles. 3 The overall reaction is a tandem Michael addition and a Thorpe-Ziegler type reaction (an enol addition to a cyano group) followed by tautomerization. 3 It should be pointed out that these compounds may exist in the 1,4-dihydro or 2,4-dihydro tautomeric forms when the N1 position is unsubstituted. Although most studies assigned the 1,4-dihydro structure to these derivatives, 2-4 recent X-ray crystallographic data prefer the 2,4-dihydro tautomer. 5,6 Since benzylidenemalononitriles may be synthesized in situ from aromatic aldehydes and malononitrile under the reaction conditions, these compounds may also be synthesized through a three-component reaction of 2-pyrazolin-5-ones, malononitrile, and aromatic aldehydes. 4,5 Most recently, a four-component synthesis by using hydrazine hydrate, acetoacetate, malononitrile, and aromatic aldehydes has also been demonstrated. 6 Initially we studied the synthesis with 3-methyl-2-pyrazolin-5-one (10a) and benzylidenemalononitrile (11a) as the model substrates. Several readily available cinchona alkaloid derivatives (Scheme 1) were screened as the catalysts. The results are summarized in Table 1.As shown in Table 1, when quinine (1) was used as the catalyst in CH 2 Cl 2 at rt, a yield of 80% of the product 12a was obtained with a low ee value of 23% (entry 1). In contrast, when cupreine (2) was used as the catalyst, product 12a was obtained in high yield of 92% with an excellent ee value of 96% (entry 2). Nevertheless, 9-epi-cupreine (3) leads to a lower ee value of 65% (entry 3). When 9-epi-amino-9-deoxyquinine (4) was applied as the catalyst, a racemic product was obtained (entry 4). Similarly, poor enantioselectivities were achieved with quinine-derived thiourea catalysts 5-7 (entries 5-7). A low ee value of 22% for the opposite enantiomer was also obtained when quinidine (8) was used as the catalyst (entry 8). It is most surprising that cupreidine (9), the pseudo-enantiomer of cupreine (2), also leads to poor enantioselectivity of the other enantiomer (6%, entry 9). Thus, this screening identified cupre...

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confidence: 99%

Organocatalyzed enantioselective synthesis of 6-amino-5-cyanodihydropyrano[2,3-c]pyrazoles

Gogoi

Zhao

2009

Tetrahedron Letters

178

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“…The 2-amino-4-substituted pyrano [2,3-c] pyrazole-3-carbonitriles were obtained in 1974 by addition of malanonitrile to arylidene-3-methyl-2-pyrazolin-5-one [7]. Later on a number of synthetic methods were developed for the synthesis of pyrano pyrazoles, using arylidenemalanionitriles and 3-methyl-5-pyrazolone [8] or 4-arylidine-3-methyl-5-pyrazolone and malanonitrile [9], and also by the three component condensation of aromatic aldehydes, malanonitriles and 3-methyl-5-pyrazolone [10]. Pyranopyrazoles are also synthesized by the condensation of two components [11].…”

Section: Introductionmentioning

confidence: 99%

DABCO catalyzed rapid one-pot synthesis of 1,4-dihydropyrano [2,3-c] pyrazole derivatives in aqueous media

Waghmare¹,

Pandit²

2017

Journal of Saudi Chemical Society

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A simple and efficient protocol is developed for the synthesis of dihydropyrano[2,3-]pyrazole derivatives by a one pot, four component reaction of ethylacetoacetate, hydrazine hydrate, malanonitrile and various aldehydes in the presence of catalytic amount of DABCO in aqueous medium. This method provides several advantages such as high yield, shorter reaction time, mild reaction condition, operational simplicity, easy work-up procedure with environment friendly nature and purification of products by non-chromatographic methods have been developed.

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“…After this Otto had proposed the synthesis of the dihydropyrano [2,3-c] 15 . Sharanin and research group have developed a three-component reaction between pyrazolone, an aldehyde and malononitrile in ethanol using triethylamine as the catalyst 16 . Kappusami and co-workers have developed solvent-free multicomponent synthesis of pyranopyrazoles using per-6-amino-β-cyclodextrin as a catalyst 17 .…”

Section: Introductionmentioning

confidence: 99%

A Rapid, Convient and Diversified-Multicomponent Synthesis and Characterization of Pyrano[2,3-<i>b</i>]Indoles

Ghodasara

Singala

Shah

2014

ILCPA

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ChemInform Abstract: NITRILE CYCLIZATION REACTIONS. VI. SYNTHESIS OF 2‐AMINO‐4‐(2‐FURYL)‐4H‐PYRANS

Abstract: Untersucht werden die Umsetzungen der Furfurylidenmalodinitrilderivate (Ia) und der Furfurylidencyanessigesterderivate (Ib) mit den Cyclohexandionen (II), mit dem Acetessigester (IV) und dem Pyrazolon (VI), die sämtlich durch Morpholin katalysiert werden.

Cited by 21 publications

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Organocatalyzed enantioselective synthesis of 6-amino-5-cyanodihydropyrano[2,3-c]pyrazoles

Organocatalyzed enantioselective synthesis of 6-amino-5-cyanodihydropyrano[2,3-c]pyrazoles

DABCO catalyzed rapid one-pot synthesis of 1,4-dihydropyrano [2,3-c] pyrazole derivatives in aqueous media

A Rapid, Convient and Diversified-Multicomponent Synthesis and Characterization of Pyrano[2,3-<i>b</i>]Indoles

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