Pyrazolo[3,4‐<i>b</i>]pyridines

Dorn, Helmut; Zubek, Alfred

doi:10.1002/anie.196709581

Cited by 12 publications

(3 citation statements)

References 5 publications

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“…In the report [66], the investigators reproduced experiments from earlier trials [67–70] in order to establish the unambiguous structure of products of 4‐ or 6‐oxo derivatives of pyrazolo[3,4‐ b ]pyridine obtained during the reaction between aminopyrazole ( 140 ) and acetoacetic ester in boiling acetic acid. It was shown [66], that refluxing a solution of 1,3‐dimethyl‐5‐amino pyrazole ( 140 ) in glacial acetic acid led to pyrazole[3,4‐ b ]pyridin‐6‐one in a 53% yield ( 143 ).…”

Section: Synthesis Of Pyrazolo[34‐b]pyridin‐6‐ones Based On Annementioning

confidence: 99%

Synthesis of Pyrazolo[3,4‐b]pyridin‐6‐ones

Komarova¹,

Makarov²,

Граник³

et al. 2012

Journal of Heterocyclic Chem

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Section: Synthesis Of Pyrazolo[34‐b]pyridin‐6‐ones Based On Annementioning

confidence: 99%

Synthesis of Pyrazolo[3,4‐b]pyridin‐6‐ones

Komarova¹,

Makarov²,

Граник³

et al. 2012

Journal of Heterocyclic Chem

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“…[1] As shown in Figure 1, compounds LY173013 and LY186826 are antibacterial agents that are analogues of penicillin and cephalosporin. In the early preparation of LY173013 and LY186826, cycloaddition [2] between azomethine imines 1 and propiolates 2 was employed to construct their molecular skeletons and introduce the ester groups in a single step. However, this thermal cycloaddition [3] was usually performed at high temperature to produce regioisomers (for example 3a and 4 in Scheme 1) when unsubstituted propiolate (as terminal alkyne) was used as dipolarophile.…”

Section: Introductionmentioning

confidence: 99%

Copper(I) Acetate‐Catalyzed Cycloaddition between Azomethine Imines and Propiolates under Additive‐Free Conditions

Shao¹,

Zhang²,

Cheng³

et al. 2013

Eur J Org Chem

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Because propiolates easily undergo base‐catalyzed self‐Michael addition, most popular catalytic systems in CuAAC cannot be used in the cycloaddition between azomethine imines and propiolates, because such reactions usually require the use of tertiary amines as additives (as base and/or ligand). We found that this problem can be resolved simply by using copper(I) acetate as catalyst, in which the acetate serves as a ligand and is converted into acetic acid during the reaction. Thus, copper(I) acetate catalyzed cycloaddition actually proceeds under additive‐free conditions (without exogenous ligand) to efficiently give 6,7‐dihydropyrazolo[1,2‐a]pyrazolone derivatives, in which the side‐reactions and byproducts caused by basic additives are completely avoided.

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“…The reactions of 1-substituted and 4-unsubstituted 5-aminopyrazoles with 8-bifunctional reagents have been shown to afford substituted aminopyrazole derivatives which can be cyclised under a variety of reaction conditions to yield pyrazolo-[3,4-blpyridine derivatives 123. 125 Recently, Ratajazyk and SwettlZ6 showed that the reaction of 5-amino-1.3-dimethylpyrazole with ethyl acetoacetate yielded two isomeric pyrazolopyridones which were identified as their corresponding tetrahydropyrazolopyridine derivatives as well as by their IR, ' H NMR and 13c NMR spectral data.…”

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confidence: 99%

Recent Developments in Chemistry of 3(5)-Aminopyrazoles

Elnagdi¹,

Abdel-Galil²,

Riad³

et al. 1983

HETEROCYCLES

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The methods of preparation, structure, chemical properties and synthetic potentiality of 3(5)-aminopyrazoles are reported.2-Substituted 6-0x0, 6-aldehyde and 6-imino nitriles also afforded 5-aminopyrazoles on reaction with hydrazine hydrate. It should be reported, here, that the exact experimental conditions described for the synthesis of these compounds should be strictly followed. The obtained products are always contaminated with pyrazolo-r1.5-aIpyrimidine derivatives, resulting either from further reaction of the formed aminopyrazole with the 6-functional nitrile or from formation of azines prior to cyclization into the aminopyrazole. The pyrazolo[1,5-alpyrimidines become the major reaction products on slight change in the reaction conditions and also in case of the reaction of hydrazine with certain reagents. Specific examples are shown in Chart 1. HETEROCYCLES, V d 20, No 12, 1983 Chart 1The reaction of substituted hydrazines with 6-functional nitriles has been shown to afford 5-aminopyrazole derivatives. The reaction may theoretically afford either 3-amino-I-substituted pyrazoles (5) or isomeric (1). Generally arylsubstituted hydrazines afford derivatives of 6 whereas alkylsubstituted hydrazines afford the isomeric on reaction with 6-keto nitriles. Several intermediate hydrazones could be isolated in these reactions (see for example g in equations below) and could be readily cyclised into the final products. The statement reported above is though usually followed an over simplification of the problem.(g) react with hydrazines to yield 3,s-diamino-4-arylazopy+azoles (El. Similarly very recently an Israeli group53 reported that phenylmalononitrile (% afforded 3,s-diamino-4-phenylpyrazole (l6) when reacted with hydrazine hydrate.Spiro and parbaS4 have reinvestigated the reaction of benzoylacetonitrile with semicarbazide which was reported to yield the pyrazole derivative 11 and other unidentifiable product and could establish that the product which was previously assigned structure 21 is actually 3-phenyl-3-oxopropionitrile semicarbazone ( 9 The other product of mp 270'~ was shown to be the py~azolo[l,~-alpyrimidine derivative (l9). 1,l-Dialkylated hydrazines (20) have been reported to condense with 8-ketonitriles (z) to afford the corresponding hydrazone derivatives (z). Cyclisation of 22 yields the aminopyrazales z v i a dealkylation of the least strongly bonded alkyl group. 54'55 ii-Reactions of hydrazines with a,%-unsaturated nitriles An efficient route for the synthesis of 5-aminopyrazoles is the reaction of hydrazines with a,%-unsaturated nitriles. For example, 4-cyano-3-aminopyrazole (25) has been obtained, always contaminated with the 5-aminopyrazole derivative 26, by the reaction of hydrazine with ethoxymethylenemalononitrile (g). Reactions of this type have been recently reviewed and will not be discussed here any further. 44 24 --2 5 *-26 -.. Propynenitrile derivatives and allenic nitriles have recently been reported to afford aminopyrazoles on reaction with hydrazines. 56.57iii-Synthesis from hete...

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Pyrazolo[3,4‐b]pyridines

Cited by 12 publications

References 5 publications

Synthesis of Pyrazolo[3,4‐b]pyridin‐6‐ones

Synthesis of Pyrazolo[3,4‐b]pyridin‐6‐ones

Copper(I) Acetate‐Catalyzed Cycloaddition between Azomethine Imines and Propiolates under Additive‐Free Conditions

Recent Developments in Chemistry of 3(5)-Aminopyrazoles

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