Nucleophilic addition to olefins. 18. Kinetics of the addition of primary amines and .alpha.-effect nucleophiles to benzylidene Meldrum's acid

The reaction of thiomethoxybenzylidene Meldrum's acid (5-SMe) with thiolate and alkoxide ion nucleophiles is shown to proceed by the two-step addition-elimination SNV mechanism in which the tetrahedral intermediate accumulates to detectable levels. For the reactions with thiolate ions, rate constants for nucleophilic addition (k1RX), its reverse (k-1RX), and for conversion of the intermediate to products (k2RX) were determined. For the reactions with alkoxide ions, only k1RX and k-1RX could be obtained; the intermediate in these reactions did not yield the expected substitution products, and hence no k2RX values could be determined. The reactions with OH- and water are believed to follow the same mechanism, but the respective intermediates remain at steady-state levels, and only k1OH and k1H²O for nucleophilic attack on 5-SMe were measurable. New insights regarding structure-reactivity behavior in SNV reactions are gained from comparisons of rate and equilibrium constants in the reactions of 5-SMe with the corresponding parameters in the reactions of methoxybenzylidene Meldrum's acid (5-OMe) and benzylidene Meldrum's acid (5-H). In particular, the relative importance of steric and pi-donor effects of the MeS vs. MeO group in 5-SMe and 5-OMe, respectively, and their role in affecting the intrinsic rate constants for nucleophilic addition, has been clarified by these comparisons. Our results also add support to a previous suggestion that soft-soft type interactions tend to increase intrinsic rate constants for thiolate ion addition to vinylic substrates, especially 5-SMe with the soft MeS group.Key words: nucleophilic vinylic substitution, intrinsic rate constants, transition state imbalances, steric/pi-donor/anomeric effects.

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ChemInform Abstract: Nucleophilic Addition to Olefins. Part 18. Kinetics of the Addition of Primary Amines and α-Effect Nucleophiles to Benzylidene Meldrum′s Acid.

Chemischer Informationsdienst ◽

10.1002/chin.198652056 ◽

1986 ◽

Vol 17 (52) ◽

Author(s):

C. F. BERNASCONI ◽

C. J. MURRAY

Keyword(s):

Nucleophilic Addition ◽

Primary Amines ◽

Kinetics Of

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Reactions of α-isobutyl-α-(methylthio)methylene Meldrum's acid with primary amines in aqueous DMSO

Canadian Journal of Chemistry ◽

10.1139/v06-166 ◽

2006 ◽

Vol 84 (12) ◽

pp. 1679-1685 ◽

Cited By ~ 1

Author(s):

Supriya Biswas ◽

Mahammad Ali ◽

Zvi Rappoport ◽

Hatim Salim

Keyword(s):

Second Order ◽

Base Catalysis ◽

Primary Amines ◽

Meldrum's Acid ◽

Meldrum’S Acid ◽

Amine Concentration ◽

First Order ◽

Acid Base Equilibrium ◽

Vinylic Substitution ◽

Step Mechanism

The aminolysis of α-isobutyl-α-(methylthio)methylene Meldrum's acid 7 with primary amines, namely, n-butylamine, glycinamide, and methoxyethylamine in DMSO–H2O (50:50, v/v) at 20 °C is overall second-order but first-order in both 7 and amines. The reaction with aminoacetonitrile (AA) is overall third-order, first-order in substrate, and second-order in amine at low amine concentration, while at high amine concentration and high pH the dependence on amine is first-order. A general three-step mechanism has been proposed for all these reactions. For the former group of amines, the first step is a rate-limiting attack of the amine to form the tetrahedral intermediate (TA±), followed by a fast acid–base equilibrium and a fast RNH3+- or H2O-assisted leaving group expulsion. For AA, general base catalysis was confirmed from the dependence of kA on [AA]f and on [OH–]. For all four amines, a good Brønsted plot of log k1 vs. pKaAH in DMSO–H2O (50:50, v/v) with βnuc = 0.34 ± 0.02 was observed. These observations are consistent with the suggested mechanism.Key words: nucleophilic vinylic substitution reactions, primary amines, α-isobutyl-α-(methylthio)methylene Meldrum's acid, three-step mechanism.

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Nucleophilic addition to olefins. 2. Reaction of benzylidene Meldrum's acid with water, hydroxide ion, and aryloxide ions. Complete kinetic analysis of the hydrolytic cleavage of the carbon:carbon double bond

Journal of the American Chemical Society ◽

10.1021/ja00524a022 ◽

1980 ◽

Vol 102 (4) ◽

pp. 1361-1366 ◽

Cited By ~ 14

Author(s):

Claude F. Bernasconi ◽

Gianni D. Leonarduzzi

Keyword(s):

Double Bond ◽

Kinetic Analysis ◽

Nucleophilic Addition ◽

Hydrolytic Cleavage ◽

Meldrum's Acid ◽

Meldrum’S Acid ◽

Hydroxide Ion

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An Expeditious One-Pot Three-Component Synthesis of 4-Aryl-3,4-dihydrobenzo[g] quinoline-2,5,10(1H)-triones under Green Conditions

Current Organic Chemistry ◽

10.2174/1385272823666191108123330 ◽

2020 ◽

Vol 23 (23) ◽

pp. 2626-2634

Author(s):

Saiedeh Kamalifar ◽

Hamzeh Kiyani

Keyword(s):

Reaction Medium ◽

Meldrum's Acid ◽

Meldrum’S Acid ◽

One Pot ◽

One Pot Synthesis ◽

Substituted Benzaldehydes ◽

High Yields ◽

First Time ◽

Green Conditions

: An efficient and facial one-pot synthesis of 4-aryl-3,4-dihydrobenzo[g]quinoline- 2,5,10(1H)-triones was developed for the first time. The process proceeded via the three-component cyclocondensation of 2-amino-1,4-naphthoquinone with Meldrum’s acid and substituted benzaldehydes under green conditions. The fused 3,4-dihydropyridin-2(1H)- one-ring naphthoquinones have been synthesized with good to high yields in refluxing ethanol as a green reaction medium. This protocol is simple and effective as well as does not involve the assistance of the catalyst, additive, or hazardous solvents.

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