scholarly journals Regio- and enantioselective umpolung gem-difluoroallylation of hydrazones via palladium catalysis enabled by N-heterocyclic carbene ligand

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shuai Huang ◽  
Fei-Fei Tong ◽  
Da-Chang Bai ◽  
Gao-Peng Zhang ◽  
Yang-Jie Jiang ◽  
...  
Keyword(s):  
Carbonyl Compounds ◽  
Acid Catalysis ◽  
Palladium Catalysis ◽  
Side Reactions ◽  
Reaction Products ◽  
Metal Catalysis ◽  
Carbon Centers ◽  
Chiral Carbon ◽  
Mechanism Of The Reaction ◽  
Sphere Mechanism

AbstractThe enantioselective construction of C–CF2R (R: alkyl or fluoroalkyl) bonds has attracted the attention of synthetic chemists because of the importance of chiral fluorinated compounds in life and materials sciences. Catalytic asymmetric fluoroalkylation has mainly been realized under organocatalysis and Lewis acid catalysis, with substrates limited to carbonyl compounds. Few examples using transition-metal catalysis exist, owing to side reactions including decomposition and isomerization of fluoroalkylating reagents. Herein we report umpolung asymmetric difluoroallylation of hydrazones with 3-bromo-3,3-difluoropropene (BDFP) under palladium catalysis. Difluoroallylation products having quaternary chiral carbon centers are afforded in good yields with high α/γ- and enantioselectivities. The usefulness of the reaction products is demonstrated and an inner-sphere mechanism of the reaction is proposed. The use of chiral N-heterocyclic carbene as ligand is the key for the selectivities as well as the productivity of the reaction.

scholarly journals Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates

2019 ◽  
Vol 377 (6) ◽  
Author(s):  
Samson Afewerki ◽  
Armando Córdova
Keyword(s):  
Transition Metal ◽  
Metal Complex ◽  
Carbonyl Compounds ◽  
Transition Metal Catalysis ◽  
Chemical Transformations ◽  
Considerable Effort ◽  
Metal Catalysis ◽  
First Report ◽  
Wide Range ◽  
Selective Chemical

AbstractThe concept of merging enamine activation catalysis with transition metal catalysis is an important strategy, which allows for selective chemical transformations not accessible without this combination. The amine catalyst activates the carbonyl compounds through the formation of a reactive nucleophilic enamine intermediate and, in parallel, the transition metal activates a wide range of functionalities such as allylic substrates through the formation of reactive electrophilic π-allyl-metal complex. Since the first report of this strategy in 2006, considerable effort has been devoted to the successful advancement of this technology. In this chapter, these findings are highlighted and discussed.

Pentacarbonylmanganese enolate and dienolate complexes. Preparative and mechanistic considerations

1990 ◽  
Vol 68 (3) ◽  
pp. 492-501 ◽  
Author(s):  
Andrew P. Masters ◽  
Ted S. Sorensen
Keyword(s):  
Nmr Spectroscopy ◽  
Nucleophilic Substitution ◽  
Reaction Products ◽  
Organic Products ◽  
Mechanism Of The Reaction ◽  
Model Reactions ◽  
Inorganic And Organic

Reactions of pentacarbonyl manganate anion with 4-halocrotonate esters or 2-halocarboxylate esters result in a complex set of inorganic and organic products, usually including the expected dienolate (or enolate) complexes. The reaction variables include the counterion, solvent, and halo group. The mechanism of the reaction has been investigated by conducting a thorough characterization of the reaction products under various conditions and also by carrying out model reactions. One can rationalize most of the non-organometallic products using either a radical or carbanion mechanism, but the latter seems to fit the available data better. Experimental procedures for optimizing the yield of the organometallic dienolate or enolate complexes have been worked out. Keywords: pentacarbonyl manganate, metalate nucleophilicity, enolate complex, nucleophilic substitution, 55Mn NMR spectroscopy.

Chemistry of kojic acid: One-step syntheses of benzothiazoles and other fused heterocycles from kojic acid derivatives

1983 ◽  
Vol 36 (11) ◽  
pp. 2307 ◽  
Author(s):  
T Teitei
Keyword(s):  
Kojic Acid ◽  
Benzyl Ether ◽  
Pyridine Derivatives ◽  
Reaction Products ◽  
Fused Heterocycles ◽  
One Step ◽  
Mechanism Of The Reaction

The reactions of the benzyl ether (1b) of kojic acid (la) and its chloromethyl derivative (1c) were investigated as new routes to fused heterocyclic systems. The chloromethyl compound proved the more versatile intermediate yielding benzothiazoles with thiourea and pyrido[l,2-a]benzimidazoles (11) and pyrido[1,2-alindole (12b) with pyridine derivatives. A number of methylated products of the benzothiazole were prepared in order to establish the structures of the reaction products and a possible mechanism of the reaction is discussed.

Enantioselective Synthesis of Polycyclic γ-Lactams with Multiple Chiral Carbon Centers via Ni(0)-Catalyzed Asymmetric Carbonylative Cycloadditions without Stirring

2019 ◽  
Vol 142 (3) ◽  
pp. 1594-1602 ◽  
Author(s):  
Keita Ashida ◽  
Yoichi Hoshimoto ◽  
Norimitsu Tohnai ◽  
David E. Scott ◽  
Masato Ohashi ◽  
...  
Keyword(s):  
Enantioselective Synthesis ◽  
Carbon Centers ◽  
Chiral Carbon

Nanogold(0)-Catalyzed Addition of Heteroelement σ Linkages to Functional Groups

Synthesis ◽  
2019 ◽  
Vol 51 (12) ◽  
pp. 2435-2454 ◽  
Author(s):  
Manolis Stratakis ◽  
Ioannis N. Lykakis
Keyword(s):  
Functional Groups ◽  
Carbonyl Compounds ◽  
Au Nanoparticles ◽  
Future Perspectives ◽  
Metal Catalysis ◽  
Dehydrogenative Coupling ◽  
Catalytic Sites ◽  
Diazo Carbonyl Compounds ◽  
Aromatic Carbonyl Compounds ◽  
Subsequent Addition

In recent years, supported Au nanoparticles and nanoporous Au materials have shown remarkable catalytic activity in the activation of σ heteroelement linkages such as, Si–H, Si–Si, B–B and B–Si, and their subsequent addition to functional groups, primarily π bonds. In this review article we discuss the reaction modes known to date, and attempt to discuss the mechanistic clues of these transformations which are rather unexpected in terms of conventional transition-metal catalysis concepts, given that the catalytic sites are metallic Au(0).1 Introduction2 Activation of Hydrosilanes2.1 Reactions of Hydrosilanes with Alkynes2.1.1 Hydrosilylation2.1.2 Dehydrogenative Coupling2.2 Reactions of Hydrosilanes with Allenes2.3 Reactions of Hydrosilanes with Carbonyl Compounds and Imines2.4 Reactions of Hydrosilanes with α-Diazo Carbonyl Compounds2.5 Miscellaneous Transformations from the Nano Au-Catalyzed Activation­ of Hydrosilanes3 Activation of Disilanes3.1 Disilylation of Alkynes3.2 Reactions of 1,1,2,2-Tetramethyldisilane with Alkynes4 Activation of Diboranes4.1 Diborylation of Alkenes4.2 Diborylation of Alkynes4.3 Diborylation of Allenes4.4 Diborylation of Methylenecyclopropanes5 Activation of Silylboranes5.1 Silaboration of Alkynes5.2 Silaboration of Allenes5.3 Silaboration of Unactivated Epoxides and Oxetanes5.4 Reactions of Silylboranes with Aromatic Carbonyl Compounds6 Conclusions and Future Perspectives

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