Pd(OAc)2-catalyzed C-H activation of indoles: a facile synthesis of 3-cyanoindoles

Indoles undergo smooth cyanation with CuCN in the presence of 20 mol % Pd(OAc)₂ and 40 mol % CuBr₂ in DMF to produce a wide range of the corresponding 3-cyanoindoles in good yields with high regioselectivity.     

Fe(Cp)2PF6 catalyzed efficient Strecker reactions of ketones and aldehydes under solvent-free conditions

The synthesis of α-aminonitriles of ketones and aldehydes was performed in very short reaction times (20 min) with excellent yields in the presence of 5 mol % of Fe(Cp)₂PF₆ under solvent-free conditions.     

Direct Mannich reaction mediated by Fe(Cp)2PF6 under solvent-free conditions

Fe(Cp)₂PF₆ (5 mol %) efficiently catalyzed Mannich reaction of aldehydes, anilines, and ketones under solvent-free condition to give β-amino-ketones in high yield (up to 94%) within 30 min with anti-isomer in excess. Simple experimental conditions and product isolation procedure makes this protocol potential for the development of clean and environment-friendly strategy for the synthesis of β-amino-ketones.     

Direct reductive amination and selective 1,2-reduction of α,β-unsaturated aldehydes and ketones by NaBH4 using H3PW12O40 as catalyst

A simple and convenient procedure for direct reductive amination of aldehydes and ketones with sodium borohydride is described. The reaction has been carried out in methanol in the presence of a catalytic amount of H₃PW₁₂O₄₀ (0.5 mol %). α,β-Unsaturated aldehydes and ketones can be easily converted into the corresponding allyl alcohols by reaction with H₃PW₁₂O₄₀ (0.5 mol %)/NaBH₄.     

Osmium (VI) catalyzed chemoselective oxidation of allylic and benzylic alcohols

A mild and highly chemoselective approach to oxidation of allylic, electron rich/deficient benzylic, and heterocyclic alcohols employing catalytic quantities of K₂[OsO₂(OH)₄] (3 mol %) and chloramine-T (50 mol %) is described. The protocol offers short reaction times (25 min–2 h), controlled oxidation, and tolerance to a variety of substrates. A systematic mechanistic study based on the LC-ESI-MS/MS reveals the presence of imidotriooxoosmium species which further reacts with alcohol to give the oxidized product.     

Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst

Fe(Cp)₂BF₄ is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)₂BF₄ as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.     

Iridium-catalyzed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols with precoordination of the double bond of alcohols to iridium

A novel iridium-catalyzed oxidative esterification reaction of aliphatic aldehydes and olefinic alcohols in toluene was found under mild conditions of [IrCl(cod)]₂ (5 mol %) in combination with K₂CO₃ (10 mol %) at rt.     

Carbohydrate-based phosphines as supporting ligand for palladium-catalyzed Suzuki–Miyaura cross-coupling reaction

Carbohydrate-based mono-phosphines (1 and 2) derived from glucose have been explored as supporting ligand for palladium-catalyzed Suzuki–Miyaura reaction. The combination of phosphine to palladium in a ratio of 2:1 resulted in a longer-living system than that in a ratio of 1:1. Using K₂CO₃ as base, aryl bromides as well as active aryl chlorides can be coupled nearly quantitatively by 0.1–0.2 mol % of 1/Pd(OAc)₂ with 95–99% of isolated yields. The amount of the catalyst could be lowered to 0.01 mol % under the optimized condition with 80% yield at room temperature. The carbohydrate hydroxyl group in 1 was found to contribute to catalytic activity.     

Fe(Cp)2PF6: An efficient catalyst for cyanosilylation of carbonyl compounds under solvent free condition

An efficient method for the addition of trimethylsilyl cyanide (TMSCN) to various aldehydes and ketones has been described using Fe(Cp)₂PF₆ (2.5 mol%) as a catalyst under solvent free condition. Excellent yields of trimethylsilylether of cyanohydrin up to (94%) was achieved within 10 min.     

An efficient, high yielding protocol for the synthesis of functionalized quinolines via the tandem addition/annulation reaction of o-aminoaryl ketones with α-methylene ketones

A mild and efficient method has been developed for the condensation of 2-aminoaryl ketones with α-methylene ketones in the presence of a catalytic amount of reusable catalyst CeCl₃·7H₂O (25 mol %) at ambient temperature to afford the corresponding poly-substituted quinolines in high yields under mild conditions.     

A mild and efficient amidation of cyclic ethers catalyzed by rhodium caprylate

A small quantity of Rh₂(O₂CC₇H₁₅)₄ (2.5 mol % to 0.6 mol %) catalyzed the α-amidation of cyclic ethers under mild conditions, 35 °C, in the presence of electron-withdrawing p-chlorobenzenesulfonamide/PhI(OAc)₂ as the nitrene source, in CH₂Cl₂ for 4 h. The corresponding N-substituted amino cyclic ethers were successfully obtained in good yields (up to 87% based on 99% conversion) and compatibility with other oxidant sensitive structures in one-pot reaction.     

Palladium-catalyzed cross-coupling reaction of alkynylzincs with benzylic electrophiles

The reaction of alkynylzinc bromides with benzyl bromides or chlorides in the presence of a catalytic amount of Pd(DPEphos)Cl₂ in THF at 23 °C cleanly produces the corresponding benzylated alkynes in 73-97% yields. With 10⁻³ mol % of Pd(DPEphos)Cl₂, the maximum turnover number of 7.1 × 10⁴ has been observed for the formation of PhCCCH₂Ph.     

Acetamide/SO2Cl2 as an efficient reagent for Friedel–Craft’s acylation of aromatic compounds under ultrasonic and microwave conditions

Acetamide/SO₂Cl₂ reagent has been developed for effective Friedel–Craft’s acylation of aromatic compounds. Acylation of aromatic compounds with acetamide/SO₂Cl₂ was much more effective and faster than analogous (acetamide/SOCl₂) and (acetamide/POCl₃) reagents even under conventional conditions. However, microwave and ultrasonic assisted reactions afforded high yields of products in very short reaction times (30–40 min under sonication and 3–4 min under microwave assisted conditions).     

Preparation of 2,2-difluoro-1-trialkylsilylethenylstannanes and their cross-coupling reactions

Reaction of 2 with bis(tributyltin) in the presence of 3 mol % Pd₂(dba)₃, 6 mol % XPhos, and 30 equiv of LiBr in wet and air bubbled THF at reflux for 8 h afforded the desired products 3 in 73–74% yields. The cross-coupling reaction of 3a with aryl iodides in the presence of 10 mol % Pd(PPh₃)₄ and 10 mol % CuI afforded the coupled products 4a–p in 47–90% yields. The coupling reaction of 3b with various alkynyl bromides having aryl-, alkyl, or trialkylsilyl group also afforded the corresponding 1,3-enynes 5a–g in 61–77% yields.     

Desymmetrization of malonamides via an enantioselective intramolecular Buchwald-Hartwig reaction

A new form of enantioselective nitrogen arylation reaction is described. Beginning with symmetrical α-(2-bromobenzyl)malonamides, intramolecular palladium-catalyzed cross-coupling using a catalyst system including 3.3 mol % Pd(OAc)₂ and 6.6 mol % of the chiral biaryl monophosphine (R)-MOP, desymmetrized quinolinone products are obtained in nearly quantitative yields in enantiomeric ratios up to 88:12. This Letter represents a rare example of enantioselective Buchwald-Hartwig reaction.     

Synthesis of α-aminonitriles under mild catalytic,metal-free conditions

α-Aminonitriles have been synthesized by a Strecker synthesis from aldehydes and ketones under mild catalytic, metal-free conditions. Aromatic aldehydes (1 equiv) were reacted with aromatic and 1° or 2° aliphatic amines (1 equiv) in EtOH containing 3 mol % of NH₄Cl to give high yields of α-aminonitriles. An alternative to adding NH₄Cl as a catalyst involved the use of excess TMSCN (1 equiv) and to promote the process. The reaction was also successful under microwave conditions using excess TMSCN with no solvent. Ketones similarly reacted with aromatic amines and excess TMSCN under conventional and microwave heating, but 30 mol % of added NH₄Cl was required for optimum conversion.     

One-pot three components synthesis of O-acetylcyanohydrins with TMSCN, acetic anhydride and carbonyl compounds under solvent-free condition

One-pot three components synthesis of O-acetylcyanohydrins has been developed in the presence of B(C₆F₅)₃ as the catalyst. Variety of aldehydes or ketones reacts with TMSCN and acetic anhydride (Ac₂O) under the influence of 1 mol % of B(C₆F₅)₃ to give good to excellent yield of the products without solvent at rt.     

Recyclable N-heterocyclic carbene/palladium catalyst on graphene oxide for the aqueous-phase Suzuki reaction

Graphene oxide (GO) was functionalized with a N-heterocyclic carbene (NHC) precursor, 3-(3-aminopropyl)-1-methylimidazolium bromide ([APMIm][Br]) for the immobilization of palladium catalyst. The GO-supported NHC precursor (IMGO) formed a stable complex with Pd(OAc)₂ (GO–NHC–Pd), which showed excellent catalytic activity and fast reaction kinetics in the aqueous-phase Suzuki reaction of aryl bromides and chlorides at relatively mild conditions (1 h at 50 °C). The GO–NHC–Pd catalyst was reused several times without any loss of its catalytic activity in the Suzuki reaction of aryl bromide.     

Regioselective ortho-acetoxylation/methoxylation of N-(2-benzoylphenyl)benzamides via substrate directed C-H activation

A highly regioselective ortho-acetoxylation of N-(2-benzoylphenyl)benzamides has been achieved using a catalytic amount of Pd(OAc)₂ (10 mol %) and a stoichiometric amount of PhI(OAc)₂ in a mixture of acetic anhydride and acetic acid via C-H activation to produce the corresponding 2-acetoxybenzamides in good yields. ortho-Methoxylation has been accomplished using methanol under similar conditions.     

Silica gel supported InBr3 and InCl3: new catalysts for the facile and rapid oxidation of 2′-hydroxychalcones and flavanones to their corresponding flavones under solvent free conditions

Silica gel supported InBr₃ or InCl₃ (15-20 mol %) were explored as a new solid-support catalysts for the facile and efficient oxidation, under solvent free conditions, of 2′-hydroxychalcones and flavanones to yield the corresponding flavones in >80% yield. The catalysts are easily prepared, stable, and efficient under mild reaction conditions.