Indium(iii) as π-acid catalyst for the electrophilic activation of carbon–carbon unsaturated systems

Abstract

This review focuses on the utilization of indium(iii) as π-acid for the activation of C-C unsaturated bonds in organic synthesis. In addition to its well-known σ-coordination with carbonyl derivatives, indium(iii) undergoes efficient π-coordination with unsaturated systems to trigger nucleophilic addition. Accordingly, indium(iii) halides and salts (InX3, X = Cl, Br, I, OTf, ONf, NTf2) have been reported as useful catalysts for a broad range of carbon-carbon and carbon-heteroatom bond formation reactions, including hydrofunctionalization (hydroarylation, hydroamination, hydroalkoxylation, and hydrothiolation), enyne cycloisomerization, and related reactions. In these reactions the counterion has a significant effect on the catalytic activity, and the development of novel In(iii) complexes and the generation of highly electrophilic cationic indium(iii) species has increased its synthetic applications as a π-acid catalyst.

Synthesis of (Z)‐β‐(Carbonylamino)alkenylindium through Regioselective anti‐Carboindation of Ynamides and Its Transformation to Multisubstituted Enamides

“…The reaction profiles giving β‐(carbonylamino)alkenylindium E1 ( 4 aa ) and α‐(carbonylamino)alkenylindium E2 are shown in Figure , red and blue lines, respectively. Two types of interaction between InBr 3 and the alkyne moiety of ynamide 1 a ( A and B ) were expected . Two complexes constructed by the coordination of an alkyne moiety to InBr 3 ( A ) and the chelation of carbonyl and alkyne moieties ( B ) were optimized.…”

A Decade of Indium‐Catalyzed Multicomponent Reactions (MCRs)

“…[3] The catalytic effect of indium(III)-based catalysts is highly focused on its σ-coordination with carbonyl derivatives, although it can also be employed as a π-acid catalyst of carbon-carbon unsaturated systems, leading to its electrophilic activation. [4] frameworks or nanoparticles, a plethora of applications has been described throughout this last decade, showcasing not only the versatility of indium catalysis but also how much there is still to be explored. In the aftermath of the international year of the periodic table of the chemical elements in 2019, we navigated through the large inventory of multicomponent reactions (MCRs) to encounter the types of useful reactions leading to important target compounds (many of which are biologically active) catalyzed by this d-block post-transition metal.…”

“…The latter one is also more expensive than the halide forms and is often considered a Lewis superacid (together with indium(III) triflimidate), since the delocalization of the counterion leads to a higher exposure of the metal cation and catalytic sites, enhancing the Lewis acid properties of this metal center, which explains why in many observed cases, indium triflate outperforms the indium halides. [4,6] Over recent years, several review publications have described the relevance of indium halides, indium salts, organoindium compounds, and indium metal-organic frameworks (MOFs) in homogeneous and heterogeneous catalysis. [7] Also in the field of asymmetric catalysis, indium associated to different chiral ligands proved to be efficient for several asymmetric chemical transformations, however, its application in asymmetric MCRs is still undeveloped, with just a few examples describing diastereoselective multicomponent transformations catalyzed by indium salts, namely Mannich-type and Reformatsky-type reactions, with the stereoselectivity induced by the chiral substrates.…”

Catalytic asymmetric Nakamura reaction by gold(I)/chiral N,Nʹ-dioxide-indium(III) synergistic catalysis

“…In 2003, Nakamura and co-workers documented an indiumcatalyzed addition of 1,3-dicarbonyl compounds to unactivated 1-alkynes 23 , providing an e cient synthetic route to form 2-alkenyl-1,3-dicarbonyl compounds from abundant carbon alkynes sources. After that, In(III) [24][25][26][27][28] , Re(I) [29][30][31] , Ir(I) 32 , Pd(0) 33 , Co(II) 34 , Mn(I) [35][36] , Ru(I)-(III) 37-39 catalytic systems were discovered, all of which were racemic reports except only one example using substrates with chiral auxiliary 40 . All the above reports, the dicarbonyl compounds and alkynes need to be activated simultaneously.…”