Themed collection Selective Catalysis for Organic Synthesis

Chiral cationic Pd aqua complexes can function as acid–base catalysts to give chiral Pd enolates with the concomitant formation of a protic acid. Cooperative action of the chiral Pd enolates with the protic acid to activate electrophiles is important to promote various C–C bond-forming reactions smoothly in a highly enantioselective manner.

The use of quasi-enantiomeric substrates and ESI-MS makes it possible to determine the intrinsic enantioselectivity of chiral catalysts by monitoring catalytic intermediates, using a fast, operationally simple protocol.

Transition metal-catalyzed addition of arylboronic acids to 2-formylbenzoates afforded 3-substituted phthalides. By using SPINOL-based phosphites as ligands, a Rh(I)-catalyzed asymmetric version of such an addition reaction has been realized and up to 83% ee was achieved.

An enantioselective ZACA route to the side-chain 3 permits an efficient and convergent synthesis of (+)-scyphostatin (1).

Hydrogen bond catalyzed Mukaiyama aldol reactions of α-ketoesters proceed in high diastereo- and enantioselectivities, giving products possessing two chiral centers, of which one is a tertiary alcohol.

We describe our studies on the effect of various Lewis bases and Brønsted acids as achiral additives on the stereoselectivity of some Rh(II)-catalyzed cyclopropanations.

A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki–Miyaura cross-coupling applications are also presented.

1,6-Enynes can be cycloisomerised into allenes under gold catalysis. This transformation involves a 5-exo dig cyclisation followed by 1,5-hydride shift.

Halohydrin dehalogenase can perform enantioselective azidolysis of aromatic epoxides to 1,2-azido alcohols which are ligated to alkynes producing chiral β-hydroxy-triazoles in a one-pot procedure with excellent enantiomeric excess.

Diarylmethanes are made “on water” simply upon mixing, in water: reactants, catalyst, and a touch of TMEDA, at room temperature. Voila.

Pd/PtBu₃-catalysed intramolecular nucleophilic addition of aryl halides to α-ketoamides in the presence of nBuOH and base has been realized with high yields, providing a new, direct, and efficient synthetic strategy to obtain 3-hydroxyoxindoles.

Polycyclic indole structures, possessing fused seven-membered rings were efficiently synthesized via the Pd-catalyzed intramolecular carbopalladation-annulation of 3-(2-iodobenzyl)-indoles with alkynes.

The enantioselective hydrogenation of a series of challenging substrates, α-aryl-β-substituted acrylic acids, was realized with high efficiency and enantioselectivity (up to 96%) under the catalysis of Ir(I) complex of Spiro-based P,N ligand, SpinPHOX.

Resolution of a C₁-symmetric phospha-adamantane which has the diamondoid structure shown has been achieved and, surprisingly, its Rh complex is a selective asymmetric hydrogenation catalyst.

Silver(I) salts mediated stereospecific transformation of optically active propargylamines to axially chiral allenes with excellent enantioselectivities (17 examples with 96–99% ee; one substrate with 91% ee) without subsequent racemization.

Chiral bifunctional phase transfer catalysts introducing bis(diarylhydroxymethyl) substituents at 3,3′-positions of the chiral binaphthyl core were successfully applied to asymmetric fluorination of cyclic β-keto esters with high enantioselectivities.

The palladium-catalysed carbonylation of vinyl aziridines can give either trans- or cis-β-lactams preferentially or even the δ-lactam simply by adjusting the reaction parameters ([Pd], [CO], temperature).

A Pd-catalyzed intramolecular [3C + 2C + 2C] cycloaddition between alkylidenecyclopropanes, alkynes and alkenes is reported. The method provides synthetically relevant 5-7-5 tricyclic structures, with good chemoselectivity and complete diastereoselectivity.

The organocatalytic asymmetric Povarov reaction of N-arylimines with 2- and 3-vinylindoles has been developed. The peculiar reactivity of vinylindoles allowed the disclosure of versatile reaction manifolds for the preparation of highly enantioenriched indole derivatives.

Rh₂(S-BPTPI)₄ is an exceptionally effective catalyst for enantioselective hetero-Diels–Alder reactions between Rawal’s diene and a diverse range of aldehydes to give, after treatment with acetyl chloride, dihydropyranone derivatives in good yields and with excellent enantioselectivities.

The synthesis of (+)-orientalol F has been completed by a stereoselective gold-catalyzed [2 + 2 + 2] cycloaddition of a ketoenyne, in which the propargylic stereocenter controls the formation of three additional stereocenters.

The iron-catalyzed addition of Grignard reagents to activated vinyl cyclopropanes proceeds in a highly regioselective fashion for branched primary, secondary and tertiary alkyl Grignard reagents. The observed selectivity likely results from a direct addition mechanism as opposed to single electron transfer or an iron-allyl based process.

Cationic [(tmeda)Pd(OEt₂)(Me)][B(Ar_F)₄] was synthesized and allowed for the first time the nature of the propagating species in the vinyl addition polymerization of norbornene to be discerned. In this system γ-agostic interactions stabilize the propagating species and permit stepwise monomer insertions to be observed by ¹H NMR spectroscopy.

A highly regioselective, one-pot sequential iodination–copper-catalyzed cross-coupling of arene C–H bonds has been developed affording an efficient method for biaryl synthesis.

Regioselective synthesis of halohydrin esters was achieved by (1) the reaction of acyl halides with epoxides and (2) the rhodium-catalyzed three-component coupling reaction of alkyl halides, carbon monoxide, and epoxides.

By establishing both a highly efficient phosphonamidate formation and a RuCp-catalyzed cleavage of an allyl linker, the solid-phase synthesis of Fmoc-(GlyP(OBn))₆-OH/DIEA, a protected form of a new type of unnatural peptide α-amino phosphonic acid oligomer (APO), has been realized.

Balloon pressure of CO is sufficient to efficiently convert a series of α-(o-haloaryl)-substituted ketones to the corresponding isocoumarins under the action of palladium catalysis.

Synthesis of five-coordinate boryl complexes that react directly with arenes at ambient temperature provides the first glimpse of the fundamental step in Ir-catalyzed C–H borylation.

Treatment of N-allylacetamide with aryl halide in the presence of sodium t-butoxide and a palladium catalyst leads to arylative cyclisation to provide the corresponding benzyl-substituted oxazoline in high yield.

4-Substituted oxazolines, which are readily synthesized from naturally occurring α-amino acids, are converted efficiently and stereospecifically to β-amidoaldehydes in the presence of synthesis gas and catalytic dicobalt octacarbonyl.

The Pt(II)- and Pd(II)-catalyzed ring-expansion of alkylidenecyclopropane derivatives leads to the formation of cyclobutenes in good yields. The presence of an enantiomerically pure quaternary stereocenter on the alkylidenecyclopropane gives the corresponding cyclobutenes with the same enantiomeric ratio.

We report asymmetric ring-opening reactions of meso-N-benzhydryl aziridines with anilines catalyzed by a Zr-BINOLate complex.

New C₂-symmetric tetrafluorobenzobarrelene ligands were prepared and applied successfully to the rhodium-catalyzed asymmetric addition of arylboronic acids to aromatic aldehydes giving chiral diarylmethanols in high yield with high enantioselectivity.

Using a new class of chiral iridium hydrogenation catalysts, the antitumor natural product demethyl calamenene was synthesized in four steps in >20% overall yield and high enantiomeric purity.

A new, straightforward synthesis of trifluoromethyl sulfonates, a class of virtually unexplored compounds: another surprising reaction of the hypervalent iodine reagent 1-trifluoromethyl-1,2-benziodoxol-3(1H)-one.

The first Ir-catalyzed asymmetric hydrogenations of vinyl boronates have been performed using low catalyst loadings and pressure (as low as 1 bar). Good selectivities (76–98% ee) were obtained for a range of substrates.

Enantioselective β-boration of α,β-unsaturated carbonyl compounds with up to 97% ee with bis(pinacolato)diboron was attained with chiral rhodium–bisoxazolinylphenyl acetate complexes.

Direct cross-coupling to construct sp³ C–sp³ C bonds via Fe-catalyzed benzylic C–H activation with 1-aryl vinyl acetate is described. The first Heck-type olefination of benzylic C–Hs was also observed with styrene as a reagent.

Lewis bases inhibit the rate of conversion for cycloaddition and those, like aldehydes or nitriles, cause a decrease in enantiocontrol due to the Lewis acidity of the activated complex.

Platinum(II) salts in combination with copper salts and molecular oxygen catalyse an unprecedented aerobic alkene oxidation that yields cyclic aminooxygenation products under sustainable conditions.

Iridium trisboryl complexes containing bisphosphine and bipyridine ligands and pinacolate and catecholate substituents are reported.

A stereocontrolled asymmetric synthesis of virgatusin was achieved in five steps from donor–acceptor cyclopropane 1 employing a Lewis acid-catalyzed cyclopropane–aldehyde addition reaction that constructs the tetrahydrofuran.

A homodinuclear Ni₂-Schiff base-catalyzed direct asymmetric hydroxymethylation of β-keto esters gave products in up to 94% ee with catalyst turnover number (TON) up to 940.

The silica gel absorbed amino acid salt catalyzed asymmetric intramolecular Robinson annulation reaction has been developed; up to 97% ee was obtained with this readily recoverable organocatalyst.

An asymmetric carbenoid insertion into S–H bonds catalyzed by copper–chiral spiro bisoxazoline complexes has been developed. A series of α-mercaptoesters were produced in high yields with moderate to good enantioselectivities (up to 85% ee). This result represents the best enantioselectivity in the catalytic asymmetric carbenoid S–H bond insertion reaction.

We report a new catalytic synthesis of α-pyridones and 3(2H)-isoquinolones from readily available 3-en-5-ynyl nitrones and o-alkynylphenyl nitrones; the reaction mechanism is proposed to involve iminyl ketene species through an oxygen transfer process.

Highly useful 2-halogenated benzofurans and benzothiophenes can be prepared from readily available gem-dibromoolefins using a mild, ligand-free copper catalyzed cross-coupling procedure.

Key elements reported are a very efficient microwave synthesis of [RuCp(naphthalene)][PF₆], the precursor of [RuCp(CH₃CN)₃][PF₆], and the application of Pd-catalysed asymmetric hydrogenolysis to prochiral ruthenium complexes.

A novel approach to the rapid construction of 5-7-6-5 fused tetracyclic carbocycles and heterocycles from cyclohexene-diynes and CO in just one step through Rh(I)-catalyzed [2 + 2 + 2 + 1] cycloaddition is described.

Amide formation catalyzed by the combination of an N-heterocyclic carbene and 1,2,4-triazole is achieved using α′-hydroxyenones as acylating reagents. No stoichiometric coupling reagents are required.

8-Hydroxy-6-methyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyridine is formed selectively in high yields by a one-pot tandem hydroformylation–cyclization sequence.

Selectively substituted biaryls containing a ketone unit are obtained under mild conditions in satisfactory yields through sequential intermolecular coupling involving ortho-substituted iodoarenes and ketones in the presence of palladium and norbornene as the only catalysts.

High efficiency was achieved by the use of an electronically and sterically-modified chiral diene ligand in rhodium-catalyzed asymmetric addition reactions. Asymmetric arylation of imines gave the corresponding diarylmethylamines in high yields with high enantioselectivity in the presence of 0.3 mol% of the diene–rhodium catalyst.

The enantioselective intramolecular alkylation of substituted imidazoles with enantiomeric excesses up to 98% has been accomplished by rhodium catalyzed C–H bond functionalization with (S,S′,R,R′)TangPhos as the chiral ligand.

Achiral meteoritic glycine and α-methylalanine, with hydrogen isotope (D/H) chirality, acted as the source of chirality in asymmetric autocatalysis with amplification of ee to afford highly enantioenriched 5-pyrimidyl alkanols.

The first dynamic kinetic asymmetric transformation in copper catalyzed allylic alkylation is reported, with enantioselectivities up to 92%.

Nickel/Lewis acid dual catalysis was found to effect the carbocyanation reaction of alkynes using arylacetonitriles, giving a range of triply substituted acrylonitriles.

Analysis of regiocontrol in Pd-catalysed C–H activation leads to observations of aryltrimethylsilyl activation and to superior results with urea-based substrates.

[Co(2,6-DiMeO-ZhuPhyrin)] can aziridinate both aromatic and aliphatic olefins under mild conditions in high yields and excellent enantioselectivities. The catalyst can be conveniently recycled and reused through a precipitation/filtration protocol.

2,3-Dihydro-1H-pyrazoles may be highly selectively synthesized via the Pd(0)-catalyzed coupling-cyclization reaction of 4-non-substituted 2-substituted 2,3-allenyl hydrazines with aryl iodides in moderate to good yields.

A heteroleptic catalyst is active in Rh- and Pd-mediated reactions using a 1 : 1 binaphthol-derived phosphite : C₁-symmetric phosphinamine ligand combination.

TfOH-catalyzed intramolecular carbocyclization of tethered alkynyl ketones in MeOH afforded a variety of highly substituted five-membered cyclic enones in good to excellent yields with high selectivities.

The rhodium-catalyzed intermolecular asymmetric hydroalkoxylation and hydrosulfenylation of diphenylphosphinylallenes gave chiral allylic phosphine oxides substituted with vinyl ether and thioether moieties in high yields with high enantioselectivities.

Carbon–nitrogen bond formation with a wide range of aryl halides and aqueous ammonia in the presence of catalytic amounts of cuprous oxide has been achieved. The reaction proceeds in aqueous solution and it eliminates the need for inert atmosphere, expensive catalysts and ligands, anhydrous solvents, and base or other additives.

Aryl-substituted olefins react with t-butyl nitrite and sodium borohydride in the presence of iron(II)phthalocyanine to give oximes in moderate to high yields.