Zwitterions and Zwitterion‐Trapping Agents in Isocyanide Chemistry

Shaabani, Ahmad; Sarvary, Afshin; Maleki, Ali

doi:10.1002/9783527652532.ch8

Cited by 5 publications

(3 citation statements)

References 130 publications

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“…When they are taken together, these data strongly suggest that the reactions between CO and compounds 6 are best interpreted in terms of the equilibria shown in Scheme 6, although we have not yet succeeded in collecting crystallographic data for the proposed products. Attempts to grow single crystals of 7 and 8 under CO pressure and efforts to trap both compounds by removing the isonitrile byproducts via subsequent chemical transformations (e.g., via reactions with isonitrile zwitterion-trapping agents 24 ) are ongoing in our laboratory. In the future, the latter efforts will be broadened to include isonitrile insertion or cycloaddition reactions, as such reactions are well-documented for palladium(0) catalysts 25 but unknown for palladium(I) complexes.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

The Multifaceted Palladium Chemistry of 2,2′-Diphosphinotolanes

et al. 2021

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The 2,2′-bis(diisopropylphosphino)tolane 1 was reacted with various palladium precursors to afford a surprisingly diverse array of palladium(II) and palladium(I) complexes. The conventional cationic [PCCP]PdCl+ pincer-type complex 2 was readily obtained by starting from 1 and an in situ generated PdCl+ fragment. Upon chloropalladation of 2 via reaction with a chloride source, a novel vinyl–palladium pincer complex (3) featuring a new C–Cl bond was produced quantitatively. The newly formed C–Cl bond in 3 may be cleaved by addition of AgBF4, which led to the regeneration of 2. Treatment of 1 with (MeCN)2PdCl2 afforded 3 in a single step, while the analogous reaction between 1 and [(η3-allyl)PdCl]2 did not result in chloride or allyl addition. Instead, the alkyne was attacked by one of the phosphines to afford the cationic CArY-MIC palladium complex 4 (CArY-MIC = cyclic (aryl)(ylidic) mesoionic carbene). Upon reaction of 1 with dibenzylidene acetone palladium(0) precursors, two alkynes were coupled to afford the novel palladol 5. When Pd(CNR)2 (R = t Bu, Cy) was employed instead of the latter palladium(0) precursors, yet another product was isolated: namely, a dinuclear Pd(I)–Pd(I) complex. In this complex, both palladium atoms are located within the pocket of the ligand and stabilized by isonitrile coligands (CNR with R = t Bu for 6a and R = Cy for 6b). The latter isonitriles may be exchanged reversibly for carbon monoxide, as shown by in situ NMR spectroscopy. The finding that five significantly different palladium complexes (2–6) have been isolated by starting from a single phosphino alkyne is discussed in the context of phosphino–palladium-catalyzed alkyne transformations.

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Section: ■ Results and Discussionmentioning

confidence: 99%

The Multifaceted Palladium Chemistry of 2,2′-Diphosphinotolanes

et al. 2021

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“…Then, an intramolecular aza -Wittig reaction renders the complex 7-membered heterocyclic product 70 with loss of TPPO. In this Michael reaction, the isocyanide partner behaves as an electron-donor soft-nucleophile, while the alkyne plays the role of the electron-acceptor soft-electrophile. , Nevertheless, a limitation is that the alkyne must be activated with an electron-withdrawing group to act as a suitable acceptor. A similar chemical behavior of NIITP was demonstrated later in the NIITP-catalyzed stereoselective o -vinylation of N -hydroxyimides …”

Section: Expanding the Mcr Scope With Niitpmentioning

confidence: 99%

One Reacts as Two: Applications of N-Isocyaniminotriphenylphosphorane in Diversity-Oriented Synthesis

et al. 2020

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N-Isocyaniminotriphenylphosphorane (NIITP) is a functionalized isonitrile that has been extensively applied in a variety of organic reactions during the last two decades. This Review summarizes the most important applications in organic synthesis of this versatile reactant, with the focus posed on mechanistic and methodological aspects allowing the generation of molecular diversity. NIITP combines the reactivity of isonitriles with that of phosphoranes to enable chemical transformations employed in the construction of compound libraries. Here, we cover from the initial applications of NIITP in the Nef isocyanide reaction to further derivations that render a variety of heterocyclic scaffolds. The presence of the isonitrile moiety in this singular compound makes possible the double addition of nucleophiles and electrophiles, which followed by inter(intra)molecular aza-Wittig type transformations enable several multicomponent and tandem processes. In particular, we stress the impact of NIITP in oxadiazole chemistry, from the early two-component transformations to recent examples of multicomponent reactions that take place in the presence of suitable electrophiles. In addition, we briefly describe the role of NIITP chemistry in generating skeletal and conformational diversity in cyclic peptides. The reaction of NIITP with alkynes is thoroughly revised, with particular emphasis on silver-catalyzed processes that have been developed in the last years. Biomedicinal applications of some reaction products are also mentioned along with a perspective of future applications of this reactant.

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“…The well-known biological properties of coumarins and 1,2,3-triazoles prompted us to synthesize molecules in which both nuclei exist. As a part of our ongoing research program on the isocyanide-based MCRs, here we report the synthesis of coumarin-3-carboxamides containing triazole ring 7 by a one-pot, six-component, condensation reaction of salicylaldehydes 1 , Meldrum’s acid 2 , aromatic propargyloxy aldehydes 3 , amines 4 , isocyanides 5 , and azides 6 , in the presence of catalytic amounts of Cu(OAc) 2 (10 mol %) and sodium ascorbate (20 mol %) as a reducing agent for the reduction of Cu(II) to Cu(I) in ethanol at room temperature (Scheme ). Recently, Balalaie et al synthesized coumarin-3-carboxamides containing lipophilic spacers through the U-4CR .…”

Section: Introductionmentioning

confidence: 99%

One-Pot Synthesis of Coumarin-3-carboxamides Containing a Triazole Ring via an Isocyanide-Based Six-Component Reaction

Shaabani

2014

ACS Comb. Sci.

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A facile, efficient, and environmentally friendly approach has been developed for the diversity oriented synthesis of trifunctional coumarin-amide-triazole containing compounds. A wide variety of pharmacologically significant and structurally interesting compounds were synthesized via a one-pot, six-component, tandem Knoevenagel/Ugi/click reaction sequence from readily available starting materials in ethanol at room temperature in excellent overall yields. Substituents could be independently varied at five different positions.

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Zwitterions and Zwitterion‐Trapping Agents in Isocyanide Chemistry

Cited by 5 publications

References 130 publications

The Multifaceted Palladium Chemistry of 2,2′-Diphosphinotolanes

The Multifaceted Palladium Chemistry of 2,2′-Diphosphinotolanes

One Reacts as Two: Applications of N-Isocyaniminotriphenylphosphorane in Diversity-Oriented Synthesis

One-Pot Synthesis of Coumarin-3-carboxamides Containing a Triazole Ring via an Isocyanide-Based Six-Component Reaction

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