A Highly Diastereoselective Recognition Process as the Basis for the Resolution of Palladatricyclo[4.1.0.0<sup>2,4</sup>]heptanes

Gold‐ and silver‐catalyzed novel intramolecular cycloisomerizations of nitrogen or carbon‐tethered indolylcyclopropenes to furnish biologically and pharmaceutically valuable azepino‐[4,5‐b]indole and spiro[indoline‐3,4′‐piperidine] derivatives have been developed. Both reactions exhibit high chemoselectivity and stereospecificity through completely different reaction pathways. Based on mechanistic studies, it is well demonstrated that gold and silver catalysts act differently to promote the anti‐ and syn‐addition and the steric effect of the catalysts play an important role to switch the addition mode, affording the catalyst‐controlled‐divergent synthesis.

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Gold‐ and Silver‐Catalyzed Intramolecular Cyclizations of Indolylcyclopropenes for the Divergent Synthesis of Azepinoindoles and Spiroindoline Piperidines

Zhu

Zhang

Tang

et al. 2015

ChemCatChem

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Chasing C,C‐Palladacycles

Garcı́a-López

Saura‐Llamas

2021

Eur J Inorg Chem

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The different approaches for the synthesis of C,C-palladacycles are reviewed in this manuscript. These species hold a bidentate ligand that chelates the Pd atom through two C-donor moieties. Their relevance is closely related to the fact that they are intermediates in many palladium-catalyzed transformations. Furthermore, some of them have been used as efficient catalyst in cross coupling reactions. The review is structured according to the different strategies that have been employed to achieve the synthesis of the C,C-palladacycle derivatives, starting with those involving one elemental step (such as the oxidative addition of strained CÀ C bonds to Pd(0) or the transmetalation reactions between organometallic reagents and Pd(II) precursors), and continuing with more complex processes, where at least two elementary steps of Pd chemistry are involved (for example, carbometalation of alkenes followed by a CÀ H activation process). A final section highlights some aspects of synthetic methodologies based on Pd catalysis in which one or several C,C-palladacyclic intermediates are involved.Lenarda et al. synthesized the first reported four-membered C,C-palladacycles 1 a and 1 b in 1972, [5] via the oxidative addition of 1,1,2,2-tetracyanocyclopropane to [Pd(PPh 2 R) 4 ] (R = Ph; Me) (Scheme 1). The reaction occurred with the CÀ C bond cleavage of the highly strained ring and oxidative addition of the two resulting fragments to Pd(0).

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Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

et al. 2013

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The direct asymmetric conjugate addition of a-cyanoacetates to enones generating densely functionalized a-amino acid precursors with adjacent quaternary and tertiary stereocenters is described comparing monoand bis-palladacycle catalysts. This edge article features the complementary value of mono-and bimetallic catalysis in a case study using related catalyst systems. Different major diastereomers of the 1,4-addition products are formed by the use of the planar chiral mono-and bimetallic catalyst systems and provide access to epimeric amino acid derivatives. Both catalyst types require the use of a Brønsted acid (HOAc) as a co-catalyst to avoid an undesired b-hydride elimination. Kinetic studies show that the C-C bond forming step takes place almost instantaneously with the bis-palladium complex after productive substrate coordination. This extraordinarily high reactivity for an elementary step generating a sterically demanding linkage of a quaternary and a tertiary stereocenter stresses the cooperativity of both metal centers.

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A Highly Diastereoselective Recognition Process as the Basis for the Resolution of Palladatricyclo[4.1.0.0^2,4]heptanes

Cited by 6 publications

References 18 publications

Gold‐ and Silver‐Catalyzed Intramolecular Cyclizations of Indolylcyclopropenes for the Divergent Synthesis of Azepinoindoles and Spiroindoline Piperidines

Gold‐ and Silver‐Catalyzed Intramolecular Cyclizations of Indolylcyclopropenes for the Divergent Synthesis of Azepinoindoles and Spiroindoline Piperidines

Chasing C,C‐Palladacycles

Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

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A Highly Diastereoselective Recognition Process as the Basis for the Resolution of Palladatricyclo[4.1.0.02,4]heptanes

Cited by 6 publications

References 18 publications

Gold‐ and Silver‐Catalyzed Intramolecular Cyclizations of Indolylcyclopropenes for the Divergent Synthesis of Azepinoindoles and Spiroindoline Piperidines

Gold‐ and Silver‐Catalyzed Intramolecular Cyclizations of Indolylcyclopropenes for the Divergent Synthesis of Azepinoindoles and Spiroindoline Piperidines

Chasing C,C‐Palladacycles

Asymmetric Michael additions of α-cyanoacetates by soft Lewis acid/hard Brønsted acid catalysis: stereodivergency with bi- vs. monometallic catalysts

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A Highly Diastereoselective Recognition Process as the Basis for the Resolution of Palladatricyclo[4.1.0.0^2,4]heptanes