Ruthenium(II)‐Catalyzed Protocol for Preparation of Diverse α,β‐ and β,β‐Dihaloenones from Diazodicarbonyls

Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.

     

Palladium‐Catalyzed Synthesis of (Z)‐3‐Arylthioacrylic Acids and Thiochromenones

The three‐component reaction of aryl halides, sodium sulfide pentahydrate (Na₂S⋅5 H₂O), and propiolic acid in the presence of 2.5% bis(triphenylphosphine)palladium chloride [Pd(PPh₃)₂Cl₂], 5% 1,4‐bis(diphenylphosphino)butane (dppb) and 2 equivalents of 1,8‐diazabicycloundec‐7‐ene (DBU) produces stereoselectively (Z)‐3‐arylthioacrylic acids in good yields. A study of the reaction pathway suggested that the C S bond formation between aryl halides and Na₂S⋅5 H₂O proceeded first, and the resulting intermediate reacted with propiolic acid to produce the desired product. In addition, when the resulting product was treated with acid, the respective thiochromenones were formed in good yields.     

Palladium(II)‐Catalyzed Hydration of Alkynylphosphonates to β‐Ketophosphonates

A highly efficient palladium(II)‐catalyzed hydration of a wide range of alkynylphosphonates to the corresponding β‐ketophosphonates has been developed to give high yields at 80 °C in 1, 4‐dioxane, with no acidic or alkaline cocatalysts required. The described catalytic system should provide an efficient alternative to highly toxic mercury‐catalyzed methodologies and be useful in synthetic programs.     

Synthesis of Free NH 2‐(Aminomethyl)indoles through Copper‐Catalyzed Reaction of 3‐(ortho‐Trifluoroacetamidophenyl)‐1‐propargylic Alcohols with Amines and Palladium/Copper‐ Cocatalyzed Domino Three‐Component Sonogashira Cross‐Coupling/Cyclization/Substitution Reactions

Free NH 2‐(aminomethyl)indoles have been prepared via copper‐catalyzed cyclization of 3‐(ortho‐trifluoroacetamidophenyl)‐1‐propargylic alcohols in the presence of primary or secondary amines. The synthesis has been developed into a simple and very efficient domino three‐component Sonogashira cross‐coupling/cyclization/substitution process that, omitting the isolation of 3‐(ortho‐trifluoroacetamidophenyl)‐1‐propargylic alcohols, provides access to this class of compounds by treating 2‐iodotrifluoroacetanilides, propargylic alcohols, and primary or secondary amines with a copper/palladium catalyst system.

     

A Palladium‐Catalyzed Domino Approach to 2,3‐Disubstituted Benzofurans via an Intermolecular Carbopalladation/C(sp3)−H Functionalization/Isomerization Sequence

A palladium‐catalyzed domino strategy has been developed for the synthesis of 2,3‐disubstituted benzofuran derivatives. This cascade reaction sequence involves intermolecular carbopalladation and C(sp³)−H functionalization followed by isomerization.

     

Palladium‐Catalyzed Construction of Spirooxindoles by Arylative Cyclization of 3‐(γ,δ‐Disubstituted)allylidene‐2‐Oxindoles

The palladium‐catalyzed, one‐pot arylative cyclization of 3‐(γ,δ‐disubstituted)allylidene‐2‐oxindoles afforded spirodihydronaphthalene‐2‐oxindole frameworks via an oxidative Heck arylation (Fujiwara–Moritani reaction), an allylic palladium migration, and an aryl C H bond functionalization/arylation cascade of reactions. This is a first example of the palladium‐catalyzed oxidative arylation and an aryl C H bond functionalization/arylation cascade reaction which involves an electrophilic arylative quenching of a π‐allylpalladium intermediate and a regio‐controlled aryl C H bond activation assisted by a weak palladium‐arene interaction.

     

Cationic copolymers of α,β‐poly‐(N‐2‐hydroxyethyl)‐DL‐aspartamide (PHEA) and α,β‐polyasparthylhydrazide (PAHy): synthesis and characterization

In the present study the derivatization of two water‐soluble synthetic polymers, α,β‐poly(N‐2‐hydroxyethyl)‐DL ‐aspartamide (PHEA) and α,β‐polyasparthylhydrazide (PAHy), with glycidyltrimethylammonium chloride (GTA) is described. This reaction permits the introduction of positive charges in the macromolecular chains of PHEA and PAHy in order to make easier the electrostatic interaction with DNA. Different parameters affect the reaction of derivatization, such as GTA concentration and reaction time. PHEA reacts partially and slowly with GTA; on the contrary the reaction of PAHy with GTA is more rapid and extensive. The derivatization of PHEA and PAHy with GTA is a convenient method to introduce positive groups in their chains and it permits the preparation of interpolyelectrolyte complexes with DNA. © 2000 Society of Chemical Industry     

Organocatalytic Enantioselective Aziridination of α‐Substituted α,β‐Unsaturated Aldehydes: Asymmetric Synthesis of Terminal Aziridines

The first example of a highly enantioselective organocatalytic aziridination of α‐substituted α,β‐unsaturated aldehydes is presented. The reaction is catalyzed by simple chiral amines and gives access to highly functional terminal azirdines containing an α‐tertiary amine stereocenter in high yields and enantiomeric ratios (95.5:4.5–98:2).     

A Highly Enantioselective Catalytic Domino Aza‐Michael/Aldol Reaction: One‐Pot Organocatalytic Asymmetric Synthesis of 1,2‐Dihydroquinolidines

The highly enantioselective organocatalytic domino aza‐Michael/aldol reaction is presented. The unprecedented, chiral amine‐catalyzed asymmetric domino reactions between 2‐aminobenzaldehydes and α,β‐unsaturated aldehydes proceed with excellent chemo‐ and enantioselectivity to give the corresponding pharmaceutically valuable 1,2‐dihydroquinolines derivatives in high yields with 90 to >99 % ee.     

Domino Reaction of Acyclic α,α‐Dialkenoylketene S,S‐Acetals and Diamines: Efficient Synthesis of Tetracyclic Thieno[2,3‐b]thiopyran‐Fused Imidazo[1,2‐a]pyridine/Pyrido[1,2‐a]pyrimidines

A series of unusual fused tetraheterocyclic compounds 3 , consisting of a thiopyran (ring A), a thiophene (ring B), a pyridine (ring C), and an imidazole or a pyrimidine (ring D) core, with a bridgehead nitrogen and an angular methyl group, were successfully synthesized by a catalyst‐free, one‐pot, two‐component domino reaction of 4‐(4‐methyl‐1,3‐dithiol‐2‐ylidene)‐1,7‐bis(aryl/heteroaryl)hepta‐1,6‐diene‐3,5‐dione 2 and diamines. In this reaction, up to five new bonds were formed accompanied by the C S bond cleavage of the 1,3‐dithiole ring of 2 , with water as the only by‐product.     

Stereoselective Synthesis of (E)‐ and (Z)‐Allylphosphonium Salts by Palladium‐Catalyzed Addition of Phosphine to Allene

The palladium‐catalyzed addition of phosphine to allene in the presence of methanesulfonic acid stereoselectively gives the (E)‐ or (Z)‐allylphosphonium salt. The (E)‐allylphosphonium salt is formed by performing the reaction in THF under reflux and the (Z)‐allylphosphonium salt is obtained at –10 °C. The (E)‐ and (Z)‐allylphosphonium salts are used in the Wittig olefination reaction, and their diastereoselectivities are compared.     

Palladium‐Catalyzed α‐Arylation of Methyl Sulfonamides with Aryl Chlorides

A palladium‐catalyzed α‐arylation of sulfonamides with aryl chlorides is presented. A Buchwald‐type pre‐catalyst formed with Kwong’s indole‐based ligand enabled this transformation to be compatible with a large variety of methyl sulfonamides and aryl chlorides in good to excellent yields. Importantly, under the optimized reaction conditions, only mono‐arylated products were observed. This method has been applied to the efficient synthesis of sumatriptan, which is used to treat migraines.

     

Palladium‐Catalyzed Annulation of 2‐(1‐Alkynyl)benzenamines with Disulfides: Synthesis of 3‐Sulfenylindoles

3‐Sulfenylindoles can be efficiently prepared in moderate to good yields from 2‐(1‐alkynyl)benzenamines and disulfides using the palladium/air catalytic systems. The study also provides a useful route to the synthesis of fipronil analogues.     

Palladium(II)‐Catalyzed Aerobic Intermolecular Cyclization of Acrylic Acid with Alkenes to α‐Methylene‐γ‐butyrolactones

The methodology in this article is a palladium(II)/copper(II)‐ or palladium(II)‐catalyzed intermolecular cyclization of acrylic acid with alkenes to produce α‐methylene‐γ‐butyrolactone derivatives using molecular oxygen as an environmentally benign oxidant. In this system, the carboxylato, especially trifluoroacetato, or trimethylacetato ligand, plays a quite important role to afford a high catalytic activity by suppressing the deposition of palladium(0) black.     

Organocatalytic Enantioselective Michael Reaction of Malononitrile with β,β‐Disubstituted Nitroalkenes

We have developed and optimized an enantioselective Michael reaction of malononitrile with β,β‐disubstituted nitroalkenes. This reaction was catalyzed by a cinchona alkaloid derived thiourea catalyst, producing products of high yields (up to 98 %) and stereoselectivities (up to 93 % ee). One of the adducts was used as an intermediate for the synthesis of dihydropyrrole derivative bearing a synthetically valuable quaternary chiral center.

     

Efficient Synthesis of β,γ‐Alkynyl α‐Amino Acid Derivatives by Ag(I)‐Catalyzed Alkynylation of α‐Imino Esters

The first catalytic synthesis of β,γ‐alkynyl α‐amino acid derivatives was achieved by direct addition of terminal alkynes to α‐imino esters in the presence of an Ag(I) salt under mild reaction conditions.     

An Efficient Domino Synthesis of Quinoxalin‐2(1H)‐ones via an SNAr/Coupling/Demesylation Reaction Catalyzed by Copper(I) as Key Step

An efficient copper‐catalyzed method for the synthesis of quinoxalin‐2(1 H)‐ones derivatives via domino S_NAr/coupling/demesylation reaction of N‐(2‐halophenyl)methylsulfonamides with 2‐halo amides has been developed. Various quinoxalinones with diversity at three positions on their scaffold have been obained, and the method is valuable for the construction of this kind of molecules with biological and pharmaceutical activities.     

Michael Reaction of Nitroalkanes with β‐Nitroacrylates under a Solid Promoter: Advanced Regio‐ and Diastereoselective Synthesis of Nitro‐Functionalized α,β‐Unsaturated Esters and 1,3‐Butadiene‐2‐carboxylates

A new class of nitro‐functionalized α,β‐unsaturated esters has been prepared by a regio‐ and diastereoselective Michael addition of nitroalkanes to β‐nitroacrylates, performed at room temperature, under carbonate on polymer as promoter, and in the presence of ethyl acetate as eco‐friendly solvent. Moreover, by the modular choice of the reaction conditions the method allows the synthesis of 1,3‐butadiene‐2‐carboxylates.     

The One‐Pot Wittig Reaction: A Facile Synthesis of α,β‐Unsaturated Esters and Nitriles by Using Nanocrystalline Magnesium Oxide

Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions.     

Palladium(II) Acetate‐Catalyzed Dual C–H Functionalization and C–C Bond Formation: A Domino Reaction for the Synthesis of Functionalized (E)‐Bisindole‐2‐ones from Diarylbut‐2‐ynediamides

A domino reaction of palladium(II)‐catalyzed dual C–H functionalization with subsequent intramolecular annulation is presented. This method provides a convenient synthesis of a range of symmetrical and unsymmetrical biologically important (E)‐bisindole‐2‐ones under extremely mild reaction conditions – room temperature, green oxidant and no additive. The reaction mechanism is elucidated in light of the yield values as well as additional control experiment results.