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

1986 ◽  
Vol 108 (17) ◽  
pp. 5251-5257 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Christopher J. Murray
Keyword(s):  
Nucleophilic Addition ◽  
Primary Amines ◽  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Alpha Effect ◽  
Kinetics Of

Kinetics of the Reactions of Benzylidene Meldrum's Acid with Thiolate and Alkoxide Ions in Aqueous Dimethyl Sulfoxide

1998 ◽  
Vol 63 (18) ◽  
pp. 6266-6272 ◽  
Author(s):  
Claude F. Bernasconi ◽  
Rodney J. Ketner
Keyword(s):  
Dimethyl Sulfoxide ◽  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Kinetics Of

Detection and kinetic characterization of SNV intermediates. Reactions of thiomethoxybenzylidene Meldrum's acid with thiolate ions, alkoxide ions, OH-, and water in aqueous DMSO

1999 ◽  
Vol 77 (5-6) ◽  
pp. 584-594 ◽  
Author(s):  
Claude F Bernasconi ◽  
Rodney J Ketner ◽  
Xin Chen ◽  
Zvi Rappoport
Keyword(s):  
Rate Constants ◽  
Nucleophilic Addition ◽  
Equilibrium Constants ◽  
Intrinsic Rate ◽  
Nucleophilic Attack ◽  
Meldrum's Acid ◽  
Meldrum’S Acid ◽  
Nucleophilic Vinylic Substitution ◽  
Steady State Levels ◽  
Vinylic Substitution

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.

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

2006 ◽  
Vol 84 (12) ◽  
pp. 1679-1685 ◽  
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.

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

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.

scholarly journals Cover Feature: Cp*Rh(III)‐Catalyzed C8 C−H Alkylation of Quinoline N ‐Oxides with Diazo Meldrum's Acid (Eur. J. Org. Chem. 3/2021)

2021 ◽  
Vol 2021 (3) ◽  
pp. 325-325
Author(s):  
Malcolm P. Huestis ◽  
Jean‐Philippe Leclerc ◽  
Robin Larouche‐Gauthier ◽  
Samuel Aubert‐Nicol ◽  
Arun Yadav ◽  
...  
Keyword(s):  
Meldrum's Acid ◽  
Meldrum’S Acid
Sign in / Sign up

Export Citation Format

Share Document