ChemInform Abstract: New Methods and Reagents in Organic Synthesis. Part 89. Studies on Reaction Conditions and New Entry to Chiral Ligands in the Chiral Lithium Amide-Mediated Enantioselective Aldol Reaction.

The use of proline-based organocatalysts has acquired significant importance in organic synthesis, especially in enantioselective synthesis. Proline and its derivatives are proven to be quite effective chiral organocatalysts for a variety of transformations including the aldol reaction, which is considered as one of the important C-C bond forming reactions in organic synthesis. The use of chiral organocatalysts has several advantages over its metal-mediated analogues. Subsequently, a large number of highly efficient proline-based organocatalysts including polymer-supported chiral analogues have been identified for aldol reaction. The use of polymer-supported organocatalysts exhibited remarkable stability under the reaction conditions and offered the best results particularly in terms of its recyclability and reusability. These potential benefits along with its economic and green chemistry advantages have led to the search for many polymer-supported proline catalysts. In this review, recent developments in exploring various polymer immobilized proline-based chiral organocatalysts for asymmetric aldol reactions are described.

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Urea-Catalyzed Functionalization of Unactivated C–H Bonds

10.26434/chemrxiv.11886789.v1 ◽

2020 ◽

Cited By ~ 2

Author(s):

Alex L. Bagdasarian ◽

Stasik Popov ◽

Benjamin Wigman ◽

Wenjing Wei ◽

woojin lee ◽

...

Keyword(s):

Hydrogen Bonding ◽

Organic Synthesis ◽

High Energy ◽

Acid Catalysts ◽

Potential Utility ◽

New Paradigm ◽

Lewis Acid Catalysts ◽

Reaction Conditions ◽

Highly Active ◽

Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp2 carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.

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Urea-Catalyzed Functionalization of Unactivated C–H Bonds

10.26434/chemrxiv.11886789 ◽

2020 ◽

Author(s):

Alex L. Bagdasarian ◽

Stasik Popov ◽

Benjamin Wigman ◽

Wenjing Wei ◽

woojin lee ◽

...

Keyword(s):

Hydrogen Bonding ◽

Organic Synthesis ◽

High Energy ◽

Acid Catalysts ◽

Potential Utility ◽

New Paradigm ◽

Lewis Acid Catalysts ◽

Reaction Conditions ◽

Highly Active ◽

Acidic Nature

Herein we report the 3,5bistrifluoromethylphenyl urea-catalyzed functionalization of unactivated C–H bonds. In this system, the urea catalyst mediates the formation of high-energy vinyl carbocations that undergo facile C–H insertion and Friedel–Crafts reactions. We introduce a new paradigm for these privileged scaffolds where the combination of hydrogen bonding motifs and strong bases affords highly active Lewis acid catalysts capable of ionizing strong C–O bonds. Despite the highly Lewis acidic nature of these catalysts that enables triflate abstraction from sp2 carbons, these newly found reaction conditions allow for the formation of heterocycles and tolerate highly Lewis basic heteroaromatic substrates. This strategy showcases the potential utility of dicoordinated vinyl carbocations in organic synthesis.

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Modern Organic Synthesis in the Laboratory

10.1093/oso/9780195187984.001.0001 ◽

2008 ◽

Cited By ~ 1

Author(s):

Jie Jack Li ◽

Chris Limberakis ◽

Derek A. Pflum

Keyword(s):

Organic Chemistry ◽

Graduate Students ◽

Organic Synthesis ◽

Functional Group ◽

Bond Formation ◽

Reaction Conditions ◽

Carbon Bond ◽

Oxidation Reduction ◽

Carbon Carbon Bond ◽

Daunting Task

Searching for reaction in organic synthesis has been made much easier in the current age of computer databases. However, the dilemma now is which procedure one selects among the ocean of choices. Especially for novices in the laboratory, it becomes a daunting task to decide what reaction conditions to experiment with first in order to have the best chance of success. This collection intends to serve as an "older and wiser lab-mate" one could have by compiling many of the most commonly used experimental procedures in organic synthesis. With chapters that cover such topics as functional group manipulations, oxidation, reduction, and carbon-carbon bond formation, Modern Organic Synthesis in the Laboratory will be useful for both graduate students and professors in organic chemistry and medicinal chemists in the pharmaceutical and agrochemical industries.

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Ligand-Driven Advances in Iridium Catalyzed sp3 C-H Borylation: 2,2’-Dipyridylarylmethane

Synlett ◽

10.1055/a-1344-1904 ◽

2020 ◽

Author(s):

Margaret R Jones ◽

Nathan D. Schley

Keyword(s):

Recent Work ◽

Organic Synthesis ◽

Functional Group ◽

Reaction Conditions ◽

Recent Advances ◽

Additional Ligand ◽

Limited Application ◽

Hydrocarbon Substrates ◽

Phenanthroline Ligands

The field of catalytic C-H borylation has grown considerably since its founding, providing a means for the preparation of synthetically versatile organoborane products. While sp2 C-H borylation methods have found widespread and practical use in organic synthesis, the analogous sp3 C-H borylation reaction remains challenging and has seen limited application. Existing catalysts are often hindered by incomplete consumption of the diboron reagent, poor functional group tolerance, harsh reaction conditions, and the need for excess or neat substrate. These challenges acutely affect C-H borylation chemistry of unactivated hydrocarbon substrates, which has lagged in comparison to methods for the C-H borylation of activated compounds. Herein we discuss recent advances in sp3 C-H borylation of undirected substrates in the context of two particular challenges: (1) utilization of the diboron reagent and (2) the need for excess or neat substrate. Our recent work on the application of dipyridylarylmethane ligands in sp3 C-H borylation has allowed us to make contributions in this space and has presented an additional ligand scaffold to supplement traditional phenanthroline ligands.

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