Highly Enantioselective Conjugate Addition of Malonate and β-Ketoester to Nitroalkenes:  Asymmetric C−C Bond Formation with New Bifunctional Organic Catalysts Based on Cinchona Alkaloids

2004 ◽  
Vol 126 (32) ◽  
pp. 9906-9907 ◽  
Author(s):  
Hongming Li ◽  
Yi Wang ◽  
Liang Tang ◽  
Li Deng
Keyword(s):  
Bond Formation ◽  
Conjugate Addition ◽  
Cinchona Alkaloids ◽  
Organic Catalysts

scholarly journals Rate Dependence on Inductive and Resonance Effects for the Organocatalyzed Enantioselective Conjugate Addition of Alkenyl and Alkynyl Boronic Acids to β-Indolyl Enones and β-Pyrrolyl Enones

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1615
Author(s):  
Amy Boylan ◽  
Thien S. Nguyen ◽  
Brian J. Lundy ◽  
Jian-Yuan Li ◽  
Ravikrishna Vallakati ◽  
...  
Keyword(s):  
Positive Charge ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Reaction Rates ◽  
Boronic Acids ◽  
Key Factors ◽  
Resonance Contribution ◽  
Reaction Conditions ◽  
Resonance Effects ◽  
Resonance Stabilization

Two key factors bear on reaction rates for the conjugate addition of alkenyl boronic acids to heteroaryl-appended enones: the proximity of inductively electron-withdrawing heteroatoms to the site of bond formation and the resonance contribution of available heteroatom lone pairs to stabilize the developing positive charge at the enone β-position. For the former, the closer the heteroatom is to the enone β-carbon, the faster the reaction. For the latter, greater resonance stabilization of the benzylic cationic charge accelerates the reaction. Thus, reaction rates are increased by the closer proximity of inductive electron-withdrawing elements, but if resonance effects are involved, then increased rates are observed with electron-donating ability. Evidence for these trends in isomeric substrates is presented, and the application of these insights has allowed for reaction conditions that provide improved reactivity with previously problematic substrates.

scholarly journals A Remarkably Efficient Phase-Transfer Catalyzed Amination of α-Bromo-α, β-Unsaturated Ketones in Water

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Alemayehu Mekonnen ◽  
Alemu Tesfaye
Keyword(s):  
Quaternary Ammonium ◽  
Phase Transfer ◽  
Conjugate Addition ◽  
Quaternary Ammonium Salts ◽  
Cinchona Alkaloids ◽  
Ammonium Salts ◽  
Alkylation Reaction ◽  
Pt Catalysts ◽  
Unsaturated Ketones ◽  
Catalytic Performances

Tandem conjugate addition–alkylation reaction of various amines with α-bromo-α, β-unsaturated ketones resulted in near-quantitative conversions into the corresponding aziridines when the reaction was carried out in the presence of 10 mol% of phase-transfer, PT catalysts in water. Some chiral quaternary ammonium salts derived from Cinchona alkaloids were investigated as water-stable PT catalysts. The scope and limitations of the reaction have also been investigated. The catalytic performances were significantly improved in comparison with the corresponding ordinary quaternary ammonium salt catalysts, and excellent yields (81%–96%) were obtained. Although an increase in the rate of aziridination has been accomplished, no stereoselectivity was observed. The positive values of the protocol have been confirmed.

scholarly journals Michael Addition of Imidazole to α, β -Unsaturated Carbonyl/Cyano Compound

2018 ◽  
Vol 5 (1) ◽  
pp. 18-31
Author(s):  
Seetaram Mohapatra ◽  
Nilofar Baral ◽  
Nilima Priyadarsini Mishra ◽  
Pravati Panda ◽  
Sabita Nayak
Keyword(s):  
Organic Chemistry ◽  
Amino Acids ◽  
Anticancer Agents ◽  
Michael Addition ◽  
Addition Reaction ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Michael Addition Reaction ◽  
Cyano Compounds ◽  
Nitrogen Bond

Introduction: Aza-Michael addition is an important reaction for carbon-nitrogen bond formation in synthetic organic chemistry. Expalantion: Conjugate addition of imidazole to α,β-unsaturated carbonyl/cyano compounds provides significant numbers of the biologically and synthetically interesting products, such as β-amino acids and β-lactams, which have attracted great attention for their use as key intermediates of anticancer agents, antibiotics and other drugs. Conclusion: This review addresses most significant method for the synthesis of N-substituted imidazole derivatives following Michael addition reaction of imidazole to α,β-unsaturated carbonyl/cyano compounds using ionic liquid/base/acid/enzyme as catalysts from year 2007-2017.

scholarly journals Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

2019 ◽  
Vol 15 ◽  
pp. 1107-1115 ◽  
Author(s):  
Yang Liu ◽  
Julie Oble ◽  
Giovanni Poli
Keyword(s):  
Reaction Temperature ◽  
Temperature Increase ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Bond Forming ◽  
At Will

Two complementary [3 + 2] annulation protocols between 3-oxoglutarates and cyclic γ-oxy-2-cycloalkenones, simply differing on the reaction temperature, are disclosed. These domino transformations allow C–C/O–C or C–C/C–C [3 + 2] annulations at will, via an intermolecular Pd-catalyzed C-allylation/intramolecular O- or C-1,4-addition sequence, respectively. In particular, exploiting the reversibility of the O-1,4-addition step, in combination with the irreversible C-1,4-addition/decarboxylation path, the intramolecular conjugate addition step could be diverted from the kinetic (O-alkylation) to the thermodynamic path (C-alkylation) thanks to a simple temperature increase. Crucial for the success of this bis-nucleophile/bis-electrophile [3 + 2] annulation is its well-defined step chronology in combination with the total chemoselectivity of the former step. This [3 + 2] C–C/O–C bond forming annulation protocol could be also extended to 1,3,5-triketones as well as 1,3-bis-sulfonylpropan-2-one bis-nucleophiles.

scholarly journals A family of low molecular-weight, organic catalysts for reductive C–C bond formation

2015 ◽  
Vol 51 (73) ◽  
pp. 13902-13905 ◽  
Author(s):  
Saad Shaaban ◽  
Anaïs Jolit ◽  
Desislava Petkova ◽  
Nuno Maulide
Keyword(s):  
Molecular Weight ◽  
Ultraviolet Light ◽  
Bond Formation ◽  
Diazonium Salts ◽  
Low Molecular Weight ◽  
Organic Catalysts

Using only small amounts of a hydrazine catalyst, the coupling of diazonium salts to a variety of reactive partners has been achieved, without the requirement for either metal adjuvants or irradiation with visible or ultraviolet light.

Conjugate addition approach for natural product synthesis inspired by gibberellin and solanoeclepin A targets

2013 ◽  
Vol 85 (6) ◽  
pp. 1149-1160 ◽  
Author(s):  
Minoru Isobe
Keyword(s):  
Oxygen Atom ◽  
Low Temperatures ◽  
Bond Formation ◽  
Conjugate Addition ◽  
Ring Closure ◽  
Natural Product Synthesis ◽  
Partial Synthesis ◽  
Unsaturated Ketones ◽  
Cyclobutane Ring ◽  
Zinc Enolate

Trimethylzincate is known to react through conjugate addition to α,β-unsaturated ketones, but adds much faster to α,β-unsaturated esters at low temperatures. Since the intermediate zinc enolate behaves differently from that of dimethylcuprate, it offers scope for application in a partial synthesis of gibberellin A3. A second example involving vinylsulfones having an oxygen atom on the γ-carbon strongly directs incoming nucleophiles in conjugate addition mode. Heteroatom-directed conjugate addition (HADCA) provides very reactive carbanion intermediates leading to cyclobutane ring formation, necessary for synthesis of solanoeclepin A. An alternative reaction for the four-membered carbocyclic ring closure was explored to make a bond formation between the propargylic cation of Nicholas type and allyltrimethylsilane nucleophile of Hosomi–Sakurai type. This method allowed a formation of tricyclo[5.2.1.01,6]decene framework.

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