4-functionally substituted 3-heterylpyrazoles: XVIII. Intramolecular cyclization of N-[3-(2-Chlorophenyl)-4-pyrazolyl]methylamine and its N-alkyl derivatives into 4,5-dihydro-2H-pyrazolo[4,3-c]quinolines

Братенко, М. К.; Panimarchuk, O. I.; Chornous, V. A.; Вовк, М. В.

doi:10.1134/s1070428007080210

Cited by 6 publications

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“…With the sterically hindered diisopropyl amine, the major reaction product is the corresponding alcohol (see Scheme 2). 1 H and 13 C NMR spectra were recorded on a Bruker DRX 500 spectrometer (500.13 and 125.76 MHz, respectively) in CDCl 3 and DMSO d 6 . Mass spectra were measured on a Finnigan Polaris Q spectrometer (electron ionizing energy 70 eV, ionization chamber temperature 250 °C).…”

Section: Resultsmentioning

confidence: 99%

Reductive amination of ferrocenylformylpyrazoles

et al. 2010

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1 Aryl 3 ferrocenyl 4 formylpyrazoles were obtained from appropriate acetylferrocene arylhydrazones by the Vilsmeier-Haack reaction. Direct reductive amination of the resulting aldehydes with primary and secondary amines and amino acid esters in the presence of NaBH(OAc) 3 was studied.Pyrazole derivatives exhibit a wide spectrum of phar macological activity. 1 Introduction of a ferrocenyl frag ment into a heterocyclic molecule often imparts a new biological activity to it or modifies its inherent activity. For instance, ferrocene containing pyrazoles have antibac terial 2 and antitumor effects in combination with low tox icity 3 and are plant growth regulators. 4 In addition, opti cally active ferrocenylpyrazole derivatives are suitable as ligands in asymmetric catalysis and can catalyze hydroge nation, silylation, and cyanation of carbonyl compounds. 5 In the present work, we studied direct reductive ami nation of 1 aryl 3 ferrocenylpyrazole 4 carbaldehydes in reactions with primary and secondary aliphatic amines. Results and DiscussionAryl methyl ketones are easily accessible reagents for the preparation of pyrazolecarbaldehydes. The synthesis involves condensation of ketones with arylhydrazines fol lowed by intramolecular cyclization of the resulting hydrazones under the conditions of the Vilsmeier-Haack formylation (Scheme 1).Reactions of acetylferrocene (1) with phenyl and β naphthylhydrazines gave the corresponding hydrazones in high yields, which were used in room temperature re actions with three equivalents of the Vilsmeier-Haack complex (DMF-POC1 3 ) in DMF. Upon hydrolysis of the iminium salts with aqueous Na 2 CO 3 , the correspond ing 1 aryl 3 ferrocenylpyrazole 4 carbaldehydes 2a,b were isolated in 84 and 65% yields, respectively.Aldehydes and ketones react with ammonia and pri mary and secondary amines in the presence of reducing agents to give primary, secondary, and tertiary amines, respectively. These reactions are known as reductive ami nation of carbonyl compounds or reductive alkylation of amines and can be effected in direct and stepwise ways. In the former case, a carbonyl compound and an amine are mixed with an appropriate reducing agent without isolating an intermediate imine or iminium salt. In the latter case, the formation of an intermediate imine is followed by its re duction. Secondary amines from pyrazolecarbaldehydes were obtained in the second way with sodium borohydride as a reducing agent, 6 while direct reductive amination of arylformylpyrazoles has not been implemented hitherto.Using sodium borohydride as a reducing agent in di rect reductive amination of 1 aryl 3 ferrocenylpyrazole 4 carbaldehydes in different solvents and at different tem peratures, we isolated the corresponding alcohols only. Modification of sodium borohydride with the electron withdrawing cyano or acetoxy group enhances the selec Scheme 1 Ar = Ph (a), β C 10 H 7 (b) Yield (%): 84 (2a), 65 (2b)

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Section: Resultsmentioning

confidence: 99%

Reductive amination of ferrocenylformylpyrazoles

et al. 2010

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ChemInform Abstract: 4‐Functionally Substituted 3‐Heterylpyrazoles. Part 18. Intramolecular Cyclization of N‐[3‐(2‐Chlorophenyl)‐4‐pyrazolyl]methylamine and Its N‐Alkyl Derivatives into 4,5‐Dihydro‐2H‐pyrazolo[4,3‐c]quinolines (V)

et al. 2008

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Microwave‐assisted Vilsmeier‐Haack synthesis of Pyrazole‐4‐carbaldehydes

Poonam

Sood

Kumar

et al. 2019

Journal of Heterocyclic Chem

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The synthesis of 4-formylpyrazoles using Vilsmeier-Haack reagent is a common protocol in pyrazole chemistry. An efficient microwave-assisted synthesis of 4formylpyrazoles by employing Vilsmeier-Haack reagent (OPC-VH) derived from phthaloyl dichloride/dimethylformamide has been described. This method offers the advantages of operational simplicity, avoiding the use of POCl 3 as toxic reagents and reuse of the by-product in the preparation of phthaloyl dichloride.

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4-functionally substituted 3-heterylpyrazoles: XVIII. Intramolecular cyclization of N-[3-(2-Chlorophenyl)-4-pyrazolyl]methylamine and its N-alkyl derivatives into 4,5-dihydro-2H-pyrazolo[4,3-c]quinolines

Cited by 6 publications

References 0 publications

Reductive amination of ferrocenylformylpyrazoles

Reductive amination of ferrocenylformylpyrazoles

ChemInform Abstract: 4‐Functionally Substituted 3‐Heterylpyrazoles. Part 18. Intramolecular Cyclization of N‐[3‐(2‐Chlorophenyl)‐4‐pyrazolyl]methylamine and Its N‐Alkyl Derivatives into 4,5‐Dihydro‐2H‐pyrazolo[4,3‐c]quinolines (V)

Microwave‐assisted Vilsmeier‐Haack synthesis of Pyrazole‐4‐carbaldehydes

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