Phase‐Transfer‐Catalysed Synthesis of Pyrroloindolines and Pyridoindolines by a Hydrogen‐Bond‐Assisted Isocyanide Cyclization Cascade

Knipe, Peter C.; Gredičak, Matija; Cernijenko, Artiom; Paton, Robert S.; Smith, Martin D.

doi:10.1002/chem.201400192

Cited by 20 publications

(15 citation statements)

References 76 publications

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“…Subsequently, the ring‐closing nucleophilic attack of the arylamino moiety to the electrophilic imine or ester groups of 2 H ‐pyrroline intermediate Int‐II would give pyrroloindoline 58 and spirocyclic pyrroline 59 , respectively. Almost at the same time, they reported an alternative chiral phase‐transfer catalyzed intramolecular 5‐ endo ‐ dig cyclization/Mannich cascade sequence of ortho ‐isocyanophenylacetonitriles for the synthesis of pyrroloindolines [55] …”

Section: [3+2] Cycloaddition Reactions Of Isocyanides With Polarized mentioning

confidence: 99%

Catalytic Enantioselective Isocyanide‐Based Reactions: Beyond Passerini and Ugi Multicomponent Reactions

Luo

Chen

et al. 2021

Chemistry A European J

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The development of catalytic enantioselective isocyanide‐based reactions is currently of great interest because the resulting products are valuable in organic synthesis, pharmacological chemistry, and materials science. This review assembles and comprehensively summarizes the recent achievements in this rapidly growing area according to the reaction types. Special attention is paid to the advantages, limitations, possible mechanisms, and synthetic applications of each reaction. In addition, a personal outlook on the opportunities for further exploration is given at the end.

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Section: [3+2] Cycloaddition Reactions Of Isocyanides With Polarized mentioning

confidence: 99%

Catalytic Enantioselective Isocyanide‐Based Reactions: Beyond Passerini and Ugi Multicomponent Reactions

Luo

Chen

et al. 2021

Chemistry A European J

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“…From a mechanistic perspective, both polar and anionic 6π electrocyclization scenarios are conceivable: indeed, a pericyclic mechanism has been found computationally for the related cyclizations of nitrile ylides, , supported by energetic and magnetic criteria (Scheme ). We have studied the cyclizations of isocyanides, combining computation and experiment to uncover the basis for the observed reactivity …”

Section: Mechanisms Of Cation-promoted Anionic Cyclizationsmentioning

confidence: 99%

“…While formal classification of these reactions according to Baldwin's rules is straightforward, their characterization as electrocyclic (or indeed as nonelectrocyclic) is an intriguing question. Collaborations with Prof. Martin Smith have led us to consider (a) 5-endo-dig closures involving isocyanide cyclizations 17 and (b) 5-endo-trig closures involving enoate 9 and imine 18 (as studied by Tantillo) acceptors (Scheme 1). Implicit in the above classification of anionic ring closures according to Baldwin's rules is the assumption of a polar mechanism.…”

Section: ■ Introductionmentioning

confidence: 99%

Catalytic Control in Cyclizations: From Computational Mechanistic Understanding to Selectivity Prediction

Peng

Paton

2016

Acc. Chem. Res.

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This Account describes the use of quantum-chemical calculations to elucidate mechanisms and develop catalysts to accomplish highly selective cyclization reactions. Chemistry is awash with cyclic molecules, and the creation of rings is central to organic synthesis. Cyclization reactions, the formation of rings by the reaction of two ends of a linear precursor, have been instrumental in the development of predictive models for chemical reactivity, from Baldwin's classification and rules for ring closure to the Woodward and Hoffmann rules based on the conservation of orbital symmetry and beyond. Ring formation provides a productive and fertile testing ground for the exploration of catalytic mechanisms and chemo-, regio-, diastereo-, and enantioselectivity using computational and experimental approaches. This Account is organized around case studies from our laboratory and illustrates the ways in which computations provide a deeper understanding of the mechanisms of catalysis in 5-endo cyclizations and how computational predictions can lead to the development of new catalysts for enhanced stereoselectivities in asymmetric cycloisomerizations. We have explored the extent to which several cation-directed 5-endo ring-closing reactions may be considered as electrocyclic and demonstrated that reaction pathways and magnetic parameters of transition structures computed using quantum chemistry are inconsistent with this notion, instead favoring a polar mechanism. A rare example of selectivity in favor of 5-endo-trig ring closure is shown to result from subtle substrate effects that bias the reactant conformation out-of-plane, limiting the involvement of cyclic conjugation. The mode of action of a chiral ammonium counterion was deduced via conformational sampling of the transition state assembly and involves coordination to the substrate via a series of nonclassical hydrogen bonds. We describe how computational mechanistic understanding has led directly to the discovery of new catalyst structures for enantioselective cycloisomerizations. Calculations have revealed that stepwise C-C bond formation and proton transfer dictate the exclusive endo diastereoselectivity of the intramolecular Michael addition to form 2-azabicyclo[3.3.1]nonane skeletons catalyzed by primary amines. These insights have led to development of a highly enantioselective catalyst with higher atom economy than previous generations. This Account also explores transition-metal-catalyzed cycloisomerizations, where our theoretical investigations have uncovered an unexpected reaction pathway in the [5 + 2] cycloisomerization of ynamides. This has led to the design of new phosphoramidite ligands to enable double-stereodifferentiating cycloisomerizations in both matched and mismatched catalyst-substrate settings. Computational understanding of the factors responsible for the regio-, enantio-, and diasterocontrol is shown to generate tangible predictions leading to an acceleration of catalyst development for selective cyclizations.

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“…Moreover, The N–N bond of the hydrazine moiety could be readily cleaved utilizing an E1cB elimination method. , For example, N-alkylation of 3j with ethyl bromoacetate was followed by elimination at 115 °C to give γ-amino nitrile 7 in 65% yield over two steps (Scheme b). It is noteworthy that γ-amino nitriles are versatile synthetic building blocks and ubiquitous structural units present in some important medicines. − With the same reaction conditions, amino-substituted dihropyrrole 8 could be formed from 5a in 72% yield (Scheme c).…”

Section: Resultsmentioning

confidence: 99%

Iminyl-Radical-Mediated C–C Cleavage/Amination and Alkene Iminoamination Enabled by Visible-Light-Induced Cerium Catalysis

Yan

Wang

et al. 2020

ACS Sustainable Chem. Eng.

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The formation of free radicals using visible light as the energy source is of great synthetic value. Despite advances in the photoredox catalysis process using expensive Ir and Ru complexes or organic dyes, the discovery and employment of photocatalysts based on alternative, abundant, and inexpensive metal salts remain highly desired. Herein, the visible-light-induced decarboxylation of α-imino-oxy acids for the generation of iminyl radicals has been accomplished using nontoxic and inexpensive CeCl3·7H2O as the photocatalyst via the LMCT process. The iminyl-radical-mediated C–C cleavage/amination and alkene iminoamination have been achieved within this catalyst system.

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Phase‐Transfer‐Catalysed Synthesis of Pyrroloindolines and Pyridoindolines by a Hydrogen‐Bond‐Assisted Isocyanide Cyclization Cascade

Cited by 20 publications

References 76 publications

Catalytic Enantioselective Isocyanide‐Based Reactions: Beyond Passerini and Ugi Multicomponent Reactions

Catalytic Enantioselective Isocyanide‐Based Reactions: Beyond Passerini and Ugi Multicomponent Reactions

Catalytic Control in Cyclizations: From Computational Mechanistic Understanding to Selectivity Prediction

Iminyl-Radical-Mediated C–C Cleavage/Amination and Alkene Iminoamination Enabled by Visible-Light-Induced Cerium Catalysis

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