Indium Reagents Research Articles

One-Step Transformation of Aryl Diazonium Salts into Aryl Indium(III) Reagents.

A method for the conversion of diazonium salts into intrinsically nucleophilic aryl indium reagents is described. The reaction is performed using indium(I) bromide with the C-In bond being formed by the interaction of aryl radicals with the indium salt. The obtained aryl indium(III) reagents work well in the Liebeskind-Srogl cross-coupling with thioesters, affording a wide variety of aryl ketones. This two-step transformation is a general method for the acylation of diazonium salts.

Synthesis and Characterization of Tetrakis(pentafluoroethyl)indate Salts.

In the rising field of organoindium chemistry little is known about the perfluoroorganyl-substituted indium compounds. The increasing use of indium reagents is explained by their high stability and tolerance towards water and functional groups. Here we report on the synthesis of the novel tetrakis(pentafluoroethyl)indate, [In(C2 F5 )4 ]- , and its characterization in salts with the cations [Li(thf)3 ]+ , Cs+ , [PPh4 ]+ and [H14 O6 ]2+ (thf=tetrahydrofuran). To the best of our knowledge, these salts constitute the first perfluoroalkylindates and, in general, the first isolated perfluoroalkylindium compounds which are fully characterized by NMR spectroscopy, mass spectrometry, elemental analysis and X-ray diffraction analysis.

Silver Iodide‐mediated Insertion of Indium to Synthesize Water‐tolerant Organoindium Reagents and the Application in Cross‐coupling Reactions

AbstractA direct synthesis method of efficient and mild water‐resistant organoindium reagents and their cross‐coupling reactions with aryl iodide by palladium‐catalyzed was described. At room temperature, organic indium reagents were mediated by AgI, and water‐tolerant alkyl indium reagents were directly and efficiently synthesized. The cross‐coupling reaction of organic indium reagents with various aryl halides could perform smoothly with palladium catalysis. The expected products were obtained in moderate to good yields, and the best yield can reach 99 %. These reactions are promising for their high reactivity, broad applicability, and functional group tolerance.

C–O cleavage via InIII alkoxide intermediates: In situ 13C NMR analysis of the mechanism of an enantioselective in-mediated cyclopropanation reaction

Abstract The mechanism of asymmetric cyclopropanation of dibenzylideneacetone and benzylideneacetone by in situ generated allyl indium reagents in the presence of methyl mandelate as a chiral modifier has been studied by in situ 13C{1H} NMR in conjunction with 13C/2H labelling and mass spectrometry. Two indium alkoxides were identified, the first arising from indium mediated allylation of the ketone, the second arising from reaction of an in situ liberated homoallylic via a LiI mediated reaction with excess allyl indium reagent. On acidification, protonation at oxygen induces C–O rather than In–O cleavage and the incipient tertiary allylic cation is stereoselectivly allylated with approximately 90% si selectivity, via what is assumed to be a mandelate-chelated indium allyl reagent.

Cesium carbonate‐catalyzed indium insertion into alkyl iodides and their synthetic utilities in cross‐coupling reactions

A catalytic amount of cesium carbonate (10 mol%) was found to be capable of effectively catalyzing the insertion of indium powder into alkyl iodides. The thus‐generated alkyl indium reagents could readily undergo palladium‐catalyzed cross‐coupling reactions with a wide variety of aryl halides, showing compatibility to a range of important functional groups.

Preparation of Alkyl Indium Reagents by Iodine-Catalyzed Direct Indium Insertion and Their Applications in Cross-Coupling Reactions.

An efficient method for the synthesis of alkyl indium reagent by means of an iodine-catalyzed direct indium insertion into alkyl iodide in THF is reported. The thus-generated alkyl indium reagents effectively underwent Pd-catalyzed cross-coupling reactions with various aryl halides, exhibiting good compatibility to a variety of sensitive functional groups. By replacing THF with DMA and using 0.75 equiv of iodine, less reactive alkyl bromide could be used as substrate for indium insertion with equal ease.

Metallic salt-catalyzed direct indium insertion into alkyl iodides and their applications in cross-coupling reactions

An efficient method for the synthesis of alkyl indium reagents via an indium(iii) or lead(ii) halide-catalyzed direct insertion of indium into alkyl iodides is developed. NMR and ESI-MS analyses indicated the formation of a mixture of an alkyl indium dihalide (RInX2) and a dialkyl indium halide (R2InX).

Synthesis of Alkyl Indium Reagents by Using Unactivated Alkyl Chlorides and Their Applications in Palladium-Catalyzed Cross-Coupling Reactions with Aryl Halides.

An efficient method for the preparation of alkyl indium reagents by using unactivated and cheap alkyl chlorides as substrates in the presence of indium and LiI was developed. The thus-formed alkyl indium species effectively underwent palladium-catalyzed cross-coupling reactions with aryl halides with wide functional group tolerance.

Stereoselective allylation and reduction of N-tert-butanesulfinyl-α-keto aldimines

A simple methodology for the synthesis of N-tert-butanesulfinyl-α-keto aldimines from both α-keto aldehydes and carboxylic esters has been developed. The addition of an in situ formed allyl indium reagent to these chiral imines was also studied. The addition took place in a sequential manner, first to the imine group with excellent diastereoselectivity and then to the carbonyl group with lower diastereoselectivity. Ruthenium-catalyzed ring closing metathesis of the resulting 5-aminoocta-1,7-dien-4-ol derivatives provided access to 6-aminocyclohex-3-enols. Reduction of the α-keto aldimines led to N-tert-butanesulfinyl-1,2-aminoalcohols as a 1:1 diastereomeric mixture.

ChemInform Abstract: Synthesis of Acyl Alkenylindium Reagents and Their Application in the Synthesis of (Z)‐α,β‐Unsaturated Ketones via Palladium‐Catalyzed Cross‐Coupling Reaction.

AbstractHydroindation reaction of allenyl ketones with indium and indium chloride produces indium reagents (II), which undergo Pd‐catalyzed cross‐coupling reactions with aryl iodides, bromides, and triflates as well as cyclohexenyl triflates to form (Z)‐α,β‐unsaturated ketones predominantly.

Copper-Catalyzed Coupling of Indium Reagents

Copper-Catalyzed Coupling of Indium Reagents

Nonsymmetrical 3,4-dithienylmaleimides by cross-coupling reactions with indium organometallics: synthesis and photochemical studies.

The synthesis and photochemical study of novel nonsymmetrical 1,2-dithienylethenes (DTEs) with a maleimide bridge have been carried out. The synthetic approach to the DTEs was based on successive selective palladium-catalyzed cross-coupling reactions of 5-susbtituted-2-methyl-3-thiophenyl indium reagents with 3,4-dichloromaleimides. The required organoindium reagents were prepared from 2-methyl-3,5-dibromothiophene by a selective (C-5) coupling reaction with triorganoindium compounds (R3 In) and subsequent metal-halogen exchange. The coupling reactions usually gave good yields and have a high atom economy with substoichiometric amounts of R3 In. The results of photochemical studies show that these novel dithienylmaleimides undergo a photocyclization reaction upon irradiation in the UV region and a photocycloreversion after excitation in the visible region, thus they can be used as photochemical switches. ON-OFF operations can be repeated in successive cycles without appreciable loss of effectiveness in the process.

Regio- and Stereoselective Aminopentadienylation of Carbonyl Compounds

A simple and robust protocol is detailed for the preparation of enantioenriched α-substituted (1,4-pentadien-3-yl)amine derivatives. The methodology involves the addition of an in situ formed pentadienyl indium reagent to chiral tert-butylsulfinimines, previously formed in the same pot. The addition takes place with excellent γ-regio- and diastereoselectivity for a wide range of carbonyl compounds, including α-unsubstituted aldehydes and methyl alkyl ketones. The catalytic hydrogenation of the sulfinamines obtained provides a convenient access to chiral α-substituted (3-pentyl)amines. The hydroboration-oxidation of the α-(1,4-pentadien-3-yl)amine derivatives, followed by a cyclization under Mitsunobu conditions, takes place with an excellent diastereoselectivity governed by the chiral sulfinyl group.

Highly-Efficient Conversion of Primary Amides to Nitriles Using Indium(III) Triflate as the Catalyst

Indium(III) triflate, a trivalent indium reagent, was shown to be a highly-efficient catalyst for the conversion of primary amides to the corresponding nitriles. The successful reactions required 5 mol% of indium(III) triflate, and toluene was proved to be the most suitable solvent. Various amides were subjected to this method, and each produced the corresponding nitriles in excellent yields.

Oxone-Mediated Oxidative Esterification of Heterocyclic Aldehydes Using Indium(III) Triflate

Recent investigations have shown the oxone-mediated oxidative methyl esterification of benzaldehyde derivatives using methanol. The reactions were accelerated in the presence of indium(III) triflate, a trivalent indium reagent, in many cases. Based on this method of methyl esterification of benzaldehyde derivatives, we further explored an application to heterocyclic aldehydes. The reactions were examined using methanol as well as other alcohols in order to establish a suitable range.

A One-Pot Asymmetric Synthesis of Homoallylic Amines via Indium-Mediated Allylation of Hydrazones

Homoallylic amines are an important structural element of natural products and valuable synthetic building blocks in organic syntheses. The nucleophilic addition of organometallic reagents to the C=N bond is a straightforward method for the synthesis of homoallylic amines. However, due to the low reactivity of imines toward nucleophiles, more reactive nucleophiles are required for the addition reaction. Thus, there are some drawbacks to such methods including aza-enolization and competitive formation of side products. Some organometallic reagents such as allylsilanes and allylboronates have been successfully employed for the formation of homoallylic amines. Employing allylindium reagents for the synthesis of homoallylic amines is attractive as indium reagents have low toxicity and low basicity and are stable to moisture and air. Recently, various methodologies for the enantioselective allylation of imines in the presence of chiral ligands have been developed. However, the synthesis of chiral ligands is frequently difficult and requires multi-step synthesis. Diastereoselective allylation of imines bearing a chiral auxiliary is a reliable and efficient method for the synthesis of optically pure homoallylic amines. Several chiral imines have been developed for indium-mediated allylations. Since Loh and co-workers’ report, chiral N-aliphatic imines, which are derived from amino acid derivatives such as (S)-valinol and (R)-phenylglycinol, have been used for diastereoselective allylations. Yus and co-workers developed a method for the synthesis of optically pure homoallylic amines via chiral Nsulfinyl imines. Chiral imines have also been widely employed. Among the chiral imine derivatives, chiral hydrazones are the choice of chiral auxiliary due to advantages that include ease of preparation, high reactivity, and high selectivity. Although (S)-1-amino-2-methoxymethylpyrrolidine and (S)-4-phenylmethyl-oxazolidin-2-one-derived hydrazones have been employed for indium-mediated diastereoselective allylations, these auxiliaries have some drawbacks such as the use of expensive and toxic reagents and multiple steps for their synthesis. Herein, we wish to report a one-pot stereoselective allylation of aldimines bearing an L-proline moiety to afford chiral homoallylic amine derivatives in a highly stereoselective manner. A one-pot asymmetric reaction that involves aldehydes, chiral hydrazides, and an allyindium species is attractive since the reaction is simple and easy to perform as well as being both eco-friendly and rapid. Benzaldehyde was chosen as a model substrate, and Zn(ClO4)2·6H2O was chosen as the catalyst since it is known to be an efficient promoter for the formation of hydrazones. We examined the one-pot allylation with benzaldehyde, a chiral L-proline-derived hydrazide, allyl bromide and indium in the presence of 1 mol % Zn(ClO4)2 in methanol at room temperature. The reaction proceeded smoothly and was complete in 2 h affording 87% of the allylated product with a 60:40 dr (Table 1, entry 1). The reaction rate was much faster than that of the reaction performed without a catalyst (15 h). This result suggests that Zn(ClO4)2·6H2O promotes the formation of hydrazone as well as assists in the allylation of the resulting hydrazone. The same reaction performed using allyl iodide instead of allyl bromide at room temperature gave an 85% chemical yield of the product with no stereoselectivity (entry 3). However, the reaction time was shortened. As the reaction temperature was lowered, the stereoselectivity increased. When performed at −20 C, the reaction was complete in 10 h with high diastereoselectivity (entry 5). Upon changing from methanol, a polar solvent, to nonpolar solvents such as toluene, dichloromethane, or chloroform, the reaction did not proceed at −20 C. With optimized reaction conditions in hand, we investigated the scope of the reaction with various aldehydes. The results are presented in Table 2. The reaction with aromatic aldehydes that were substituted with an electron-donating

ChemInform Abstract: Synthesis of Axially Chiral 1,1′‐Binaphthalenes by Palladium‐Catalyzed Cross‐Coupling Reactions of Triorganoindium Reagents.

AbstractIn some cases increasing the amount of triorganyl indium reagent can increase the yields of the products [cf.

Synthesis of Axially Chiral 1,1′‐Binaphthalenes by Palladium‐Catalysed Cross‐Coupling Reactions of Triorganoindium Reagents

Abstract1,1′‐Binaphthalenes and heterocyclic analogues can be efficiently prepared by palladium‐catalysed cross‐coupling reactions between tri(1‐naphthyl)indium reagents and 1‐halonaphthalenes and haloisoquinolines. The reactions were usually carried out in THF at 80 °C with a slight excess of the indium reagent (40 mol‐%) and a low catalyst loading (4 mol‐% Pd) to afford the cross‐coupling products in good yields (45–99 %). The method allows the synthesis of sterically hindered 2‐substituted and 2,2′‐disubstituted 1,1′‐binaphthalenes and naphthylisoquinolines. In addition, the coupling reactions can be performed enantioselectively and the best enantiomeric excesses were obtained by using the chiral amino‐phosphane ferrocenyl ligand (R,S)‐PPFA.

The Effect of Indium(III) Triflate in Oxone-Mediated Oxidative Methyl Esterification of Aldehydes

An oxidative methyl esterification of aldehydes was effectively achieved. The trivalent indium reagent, indium(III) triflate, was revealed to accelerate the reactions in many cases. Aromatic aldehydes with various substituents were subjected to this method, and each produced the corresponding methyl esters in good to excellent yields within a relatively short reaction time.

The stereochemical outcome of allyl magnesium and indium additions to 5-substituted norbornen-7-ones and its application to cis fused carbocycle formation via ring rearrangement metathesis

The addition of allyl magnesium and allyl indium reagents to a key TBS protected norbornenyl building block, synthesised in 6-steps from commercially available 1,1-dimethoxy-2,3,4,5-tetrachlorocyclopentadiene, has been achieved providing the syn addition products with high diastereoselectivity. The subsequent exposure of the addition products to metathesis conditions, in the presence of ethene, then provided cis fused[3.0.3]-carbocycles with very high regioselectivity, via a Ring Rearrangement Metathesis (RRM) transformation.