Synergistic Catalysis: Enantioselective Ring Expansion of Vinyl Cyclopropanes Combining Four Catalytic Cycles for the Synthesis of Highly Substituted Spirocyclopentanes Bearing up to Four Stereocenters

Since the beginning of the millennium, organocatalysis has been gaining a predominant role in asymmetric synthesis and it is, nowadays, a foundation of catalysis. Synergistic catalysis, combining two or more different catalytic cycles acting in concert, exploits the vast knowledge acquired in organocatalysis and other fields to perform reactions that would be otherwise impossible. Merging organocatalysis with photo-, metallo- and organocatalysis itself, researchers have ingeniously devised a range of activations. This feature review, focusing on selected synergistic catalytic approaches, aims to provide a flavor of the creativity and innovation in the area, showing ground-breaking examples of organocatalysts, such as proline derivatives, hydrogen bond-mediated, Cinchona alkaloids or phosphoric acids catalysts, which work cooperatively with different catalytic partners.

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Synergistic catalysis: cis-cyclopropanation of benzoxazoles

Chemical Science ◽

10.1039/c5sc03597j ◽

2016 ◽

Vol 7 (2) ◽

pp. 984-988 ◽

Cited By ~ 32

Author(s):

Marta Meazza ◽

Mark E. Light ◽

Andrea Mazzanti ◽

Ramon Rios

Keyword(s):

Synergistic Catalysis ◽

Catalytic Cycles

3 catalytic cycles working in concert to generate cis cyclopropanes in good yields and stereoselectivities!

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Regio-, Stereo- and Enantioselective α-Addition of Carbonyl Nucleo-philes to Allenamides Catalyzed by a Synergistic Copper/Enamine System

10.26434/chemrxiv.11830935.v1 ◽

2020 ◽

Author(s):

Rémi Blieck ◽

Sebastien Lemouzy ◽

Marc Taillefer ◽

Florian Monnier

Keyword(s):

Catalytic System ◽

Secondary Amine ◽

Primary Amine ◽

Synergistic Catalysis ◽

Enantioselective Addition ◽

Amine Catalysts

A dual copper/enamine catalytic system is found to enable an intermolecular enantioselective α-addition of various carbonyl nucleophiles to allenamides. Secondary amine catalysts allowed the highly enantioselective addition of aldehydes, while using primary amine catalysts led to the enantioselective addition of ketoester nucleophiles. The process was found to be highly regio-, stereo- and enantio-selective and represented the first allene hydrofunctionalization using an synergistic catalysis involving copper

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Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds

10.26434/chemrxiv.11822676.v1 ◽

2020 ◽

Author(s):

Nathan O'Brien ◽

Naokazu Kano ◽

Nizam Havare ◽

Ryohei Uematsu ◽

Romain Ramozzi ◽

...

Keyword(s):

Crystal Structure ◽

Ring Expansion ◽

Bicyclic Compound ◽

Compound A ◽

Ligand System ◽

Large Bulk ◽

Rearrangement Reaction ◽

Hydride Abstraction ◽

Pentacoordinated Phosphorus ◽

Acids And Bases

<div>The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were</div><div>explored. A strong Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the</div><div>pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF</div><div>stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a</div><div>unique rearrangement reaction, that involved a two-fold ring expansion, to give an unusual fused bicyclic compound or it</div><div>could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be more reactive</div><div>towards alkynes over alkenes with good to moderate regioselectivity towards the terminal carbon. The second compound,</div><div>a phosphoranyl-triarylborate, was found to have a vastly different reactivity to the trihydroborate as it was highly stable</div><div>towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure</div>

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Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

10.26434/chemrxiv.8263415.v1 ◽

2019 ◽

Cited By ~ 3

Author(s):

Hannah E. Burdge ◽

Takuya Oguma ◽

Takahiro Kawajiri ◽

Ryan Shenvi

Keyword(s):

Intramolecular Cyclization ◽

Cross Coupling ◽

Building Blocks ◽

Ring Expansion ◽

Dual Catalysis ◽

Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

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Concise Synthesis of GB22 by Endo-Selective Siloxycyclopropane Arylation

10.26434/chemrxiv.8263415 ◽

2019 ◽

Author(s):

Hannah E. Burdge ◽

Takuya Oguma ◽

Takahiro Kawajiri ◽

Ryan Shenvi

Keyword(s):

Intramolecular Cyclization ◽

Cross Coupling ◽

Building Blocks ◽

Ring Expansion ◽

Dual Catalysis ◽

Acid Labile

<div><div><div><p>The first synthesis of GB22 was accomplished by a con- cise, modular route. Two building blocks converged in a novel sp3-sp2 attached-ring coupling that used Ir/Ni dual-catalysis to reverse the regioselectivity of siloxycy- clopropane arylation. This cross-coupling proved general to access β-substituted tetralones via ring-expansion of indanone-derived siloxycyclopropanes. The congested, bridging rings of the GB alkaloids were completed using an aluminum-HFIP complex that effected intramolecular cyclization of an acid-labile substrate.</p></div></div></div>

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Piperazine as an Inexpensive and Efficient Ligand for Pd-Catalyzed Homocoupling Reactions to Synthesize Bipyridines and Their Analogues

Current Organic Synthesis ◽

10.2174/1570179415666180913131905 ◽

2019 ◽

Vol 16 (1) ◽

pp. 173-180

Author(s):

Mingwei Chen ◽

Jinyu Hu ◽

Xiaoli Tang ◽

Qiming Zhu

Keyword(s):

Transition Metal ◽

Oxidation State ◽

Coupling Reaction ◽

Aryl Halides ◽

Metal Species ◽

Good Substrate ◽

Active Metal ◽

Homocoupling Reaction ◽

Catalytic Cycles ◽

Reductive Homocoupling

Aim and Objective: The synthesis of bipyridines, especially 2, 2’-bipyridines, remains challenging because the catalytic cycle can be inhibited due to coordination of bipyridine to transition metal. Thus, the development of efficient methods for the synthesis of bipyridines is highly desirable. In the present work, we presented a promising approach for preparation of bipyridines via a Pd-catalyzed reductive homocoupling reaction with simple piperazine as a ligand. Materials and Methods: Simple and inexpensive piperazine was used as a ligand for Pd-catalyzed homocoupling reaction. The combination of Pd(OAc)2 and piperazine in dimethylformamide (DMF) was observed to form an excellent catalyst and efficiently catalyzed the homocoupling of azaarenyl halides, in which DMF was used as the solvent without excess reductants although stoichiometric reductant was generally required to generate the low-oxidation-state active metal species in the catalytic cycles. </P><P> Results: In this case, good to excellent yields of bipyridines and their (hetero) aromatic analogues were obtained in the presence of 2.5 mol% of Pd(OAc)2 and 5 mol% of piperazine, using K3PO4 as a base in DMF at 140°C. Conclusion: According to the results, piperazine as an inexpensive and efficient ligand was used in the Pd(OAc)2-catalyzed homocoupling reaction of heteroaryl and aryl halides. The coupling reaction was operationally simple and displayed good substrate compatibility.

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