Untitled

Ravina, I.; Zicāne, Daina; Петрова, М. В.; Gudriniece, E.; Kalejs, U.

doi:10.1023/a:1020689805869

Cited by 11 publications

(5 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…116–120 °C (lit. [ 55 ] 111–114 °C). 1 H NMR (300 MHz, [D 6 ]DMSO) δ = 8.07 (d, J = 6.2 Hz, 1H), 7.68–7.62 (m, 1H), 7.41–7.38 (m, 1H), 6.92 (d, J = 6.9 Hz, 1H), 6.20 (d, J = 6.2 Hz, 1H), 2.93 (s, 3H).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

On the Regioselectivity of the Gould–Jacobs Reaction: Gas‐Phase Versus Solution‐Phase Thermolysis

Wernik

Hartmann

Sipos³

et al. 2020

Eur J Org Chem

View full text Add to dashboard Cite

A detailed investigation of the regioselectivity in the thermal cyclization of (pyridyl)aminomethylenemalonates both in the gas‐ and solution phase is presented. Flash vacuum pyrolysis (FVP) as a gas‐phase thermolysis technique is used to study the Gould–Jacobs reaction at temperatures between 450–650 °C, while different solution‐phase heating techniques (reflux, microwave, and continuous flow) were employed at 260–350 °C. Depending on the position of the substituent in the pyridine moiety and the applied thermolysis technique, the regioselectivity of the cyclization can be controlled either in favor of the kinetic (pyridopyrimidinone) or the thermodynamic (naphthyridinone) product. Under FVP conditions, 6‐substituted pyridopyrimidinones were obtained in high regioselectivity, which was not demonstrated before under standard Gould–Jacobs reaction conditions. DFT calculations have been additionally performed to provide further insights into the mechanistic pathways of this specific Gould–Jacobs reaction.

show abstract

Section: Methodsmentioning

confidence: 99%

“…The spectroscopic data are in agreement with the previously published values. [55] Synthesis of 7-Methyl-1,8-naphthyridin-4(1H)-one (8a). Into a 10 mL microwave process vial, equipped with a stir bar, were placed 7a (50 mg, 0.31 mmol) and 1.5 mL of diphenyl ether.…”

Section: Eurjoc European Journal Of Organic Chemistrymentioning

confidence: 99%

On the Regioselectivity of the Gould–Jacobs Reaction: Gas‐Phase Versus Solution‐Phase Thermolysis

Wernik

Hartmann

Sipos³

et al. 2020

Eur J Org Chem

View full text Add to dashboard Cite

show abstract

“…The precipitated 4H-pyrido [1,2-a]pyrimidin-4-ones were filtered off and recrystallized from EtOH. Our work-up protocol provided 15-30% better yields for 17f, 17i and 17k than in the earlier methods 20,21 The thermal cyclization of 3-(6-substituted-2-pyridyl)acrylates (20) Dimers 29 would be formed in a "head-to-tail" [4+2] cyclodimerization of the iminoketene 26, which would probably take place in a pseudopericyclic manner, initiated by the attack of an imino lone pair on the carbonyl carbon of a second molecule of iminoketene (Scheme 6). The initial dimer (28) thus formed would tautomerizes by 1,3 hydrogen shift to the isolated product 29.…”

Section: Resultsmentioning

confidence: 69%

Synthesis of Halogenated 4H-Pyrido[1,2-a]pyrimidin-4-ones

Molnár¹,

Faigl²,

Podányi³

et al. 2009

HETEROCYCLES

View full text Add to dashboard Cite

show abstract

“…In 2002, a series of 6(8)-methyl-, 7(9)-halo-, 8(9)ethyland 8-nitro-substituted 4H-pyrido[1,2-a]pyrimidin-4-ones [21] were obtained in 21 -74 % yields, when the pyridylaminomethylene malonates synthesized from the reactions of ethoxymethyleneisopropylidene malonate with 2-aminopyridines were heated to their melting points. Previously, 7-alkyl substituted pyridopyrimidines analogs [22] were isolated from the 2-pyridylamino-or 5-methyl-2-pyridylaminomethyleneisopropylidene malonates by also melting them.…”

Section: J Heterocyclic Chem 43 229 (2006)mentioning

confidence: 99%

New efficient approach for the synthesis of 2‐alkyl(aryl) substituted 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones

Bonacorso

Righi

Rodrigues

et al. 2006

Journal of Heterocyclic Chem

View full text Add to dashboard Cite

A new, efficient and easy route for the preparation of a series of 2-alkyl(aryl) substituted 4-oxo-4H-pyrido-[1,2-a]pyrimidines, where alkyl = CH 3 ; aryl = C 6 H 5 , 4-FC 6 H 4 , 4-ClC 6 H 4 , 4-BrC 6 H 4 , 4-CH 3 C 6 H 4 , 4-OCH 3 -C 6 H 4 , 4-NO 2 C 6 H 4 in 45 -80 % yield from the reaction of β-alkoxyvinyl trichloromethyl ketones with 2-aminopyridine under mild conditions, is then reported.J. Heterocyclic Chem., 43, 229 (2006).In the last years, the introduction of a trifluoro-or trichloromethyl group into an acyclic or cyclic compound have widely been studied and reviewed [1,2]. Consequently, these new organic structures can bring about remarkable changes in their physical, chemical and biological properties.Recently, we have also reported an addition/elimination sequence leading to trifluoroacetyl and trichloroacetyl acyclic enamines from the reaction of o-phenylenediamine [3], o-aminophenol [4], 1-naphthylamine [5] and S,Sdimethylsulfoximide [6] with 4-alkyl(aryl)-1,1,1-trihalo-4-alkoxyalken-2-ones. The acyclic enaminones, derived from o-phenylenediamine and o-aminophenol, were submitted to in vitro anti-tumor screens. It was observed that the trichloromethylated compounds exhibited a superior activity if compared to trifluoromethylated analog compounds. The best activity was obtained when the structure was derived from o-aminophenol and it presents a trichloroacetyl-and a p-bromophenyl substituent bound at the carbon-2 and -1, respectively [4].β-Alkoxyvinyl trichloromethyl ketones 1 proved also to be useful building blocks for the synthesis of five-, six-, and seven-, member trichloromethylated heterocycles [2] due to the fact that one of the best methods to introduce a trichloromethyl group into heterocycles is based on the trichloromethylated building block approach. This approach relies on the trichloroacetylation of enol ethers or acetals to give, in one step and good yields, the above cited ketones 1. On the other hand, the classical haloform reaction in which the trichloromethyl substituent is a leaving group is well developed [7] and systematic studies, involving the usefulness of the leaving group ability of the trichloromethyl in many synthetic transformations, were reported [2,[8][9][10][11][12][13][14]. However, just a few references from the literature report the use of the trichloromethyl substituent as a good leaving group in heterocyclic synthesis [15]. Furthermore, the synthetic strategy involving the ketones 1 and 2-aminopyridine was never applied in attempt to obtain regiospecificaly 2-alkyl(aryl)substituted 4H-pyrido[1,2-a]pyrimidin-4-ones under relative mild conditions.Although some researches, up to 1951, considered that the heterocycle obtained from the reaction of 2-aminopyridine with ethyl acetoacetate was 4-methyl-2H-pyrido[1,2-a]pyrimidin-2-one, Antaki and Petrow [16] showed (in 1951), that the product was, in fact, the 2-methyl-4-keto isomer. To prove this hypothesis, 2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one was obtained from the reaction of 2-bromopyridine with ethyl β-amin...

show abstract

Untitled

Cited by 11 publications

References 4 publications

On the Regioselectivity of the Gould–Jacobs Reaction: Gas‐Phase Versus Solution‐Phase Thermolysis

On the Regioselectivity of the Gould–Jacobs Reaction: Gas‐Phase Versus Solution‐Phase Thermolysis

Synthesis of Halogenated 4H-Pyrido[1,2-a]pyrimidin-4-ones

New efficient approach for the synthesis of 2‐alkyl(aryl) substituted 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones

Contact Info

Product

Resources

About