Iridium(I)-catalyzed regio- and enantioselective allylic amidation

Ir(I)-catalyzed intermolecular allylic amidation of ethyl allyl carbonates with soft nitrogen nucleophiles under completely ‘salt-free’ conditions is described. A combination of [Ir(COD)Cl]₂, a chiral phosphoramidite ligand L^∗, and DBU as a base in THF effects the reaction. The reaction appears to be quite general, accommodating a wide variety of R-groups and soft nitrogen nucleophiles, and proceeds with excellent regio- and enantioselectivities to afford the branched N-protected allylic amines. The developed reaction was conveniently utilized in the asymmetric synthesis of N-Boc protected α- and β-amino acids as well as (−)-cytoxazone.     

Asymmetric hydrogenolysis of racemic tertiary alcohols, 3-substituted 3-hydroxyisoindolin-1-ones

Asymmetric hydrogenolysis of racemic tertiary alcohols, 3-substituted 3-hydroxyisoindolin-1-ones, was developed using chiral phosphoric acid as catalyst and a Hantzsch ester as the hydrogen source with up to 95% ee. The reaction process of this asymmetric transfer hydrogenation may occur directly through the acyliminium ion intermediate.     

Rhodium(I)-catalyzed enantioselective 1,4-addition of nucleophilic silicon

A rhodium(I)-catalyzed activation of a silicon-boron linkage, that is, the transmetalation of silicon from boron to rhodium(I) by means of an Rh^I-OH complex, enables the conjugate transfer of nucleophilic silicon onto α,β-unsaturated acceptors. Pre- or in situ formed cationic rhodium(I)-binap complexes catalyze this novel carbon-silicon bond formation with exceptional enantiocontrol, 92 to >99% ee for cyclic carbonyl and carboxyl compounds as well as >99% ee for acyclic carboxyl compounds.     

Ferrocene-based bidentate phosphonite ligands for rhodium(I)-catalyzed enantioselective hydroformylation

A new class of chiral modular bidentate phosphonite ligands has been synthesized in good overall yields by using cheap trans-1,2-diaminocyclohexane and ferrocene as starting materials, and applied in the Rh(I)-catalyzed asymmetric hydroformylation of vinyl acetate and styrene to afford the corresponding optically active aldehydes with good regioselectivity (up to 16.9 b/l ratio) and moderate to good enantioselectivity (up to 83% ee). The substituents on the backbone of the ligands are found to exhibit a remarkable effect on both the regio- and enantioselectivity of the catalysis.     

Ir(I)-catalyzed intermolecular regio- and enantioselective hydroamination of alkenes with heteroaromatic amines

A cationic Ir(I)-C(3)-TUNEPHOS complex catalyzed an intermolecular hydroamination of styrene derivatives with various heteroaromatic amines. The reaction gave Markovnikov products with perfect regioselectivity and good enantioselectivity under solvent-free conditions.     

Ir(I)-catalyzed enantioselective secondary sp3 C-H bond activation of 2-(alkylamino)pyridines with alkenes

A cationic Ir(I)-tolBINAP complex catalyzed an enantioselective C-C bond formation initiated by secondary sp(3) C-H bond cleavage adjacent to a nitrogen atom. The reaction of 2-(alkylamino)pyridines with various alkenes gave chiral amines in good yields with high enantiomeric excesses.     

Asymmetric hydrogenolysis of racemic 3-substitued-3-hydroxy-isoindolin-1-ones employing SPINOL-derived chiral phosphoric acid

The asymmetric hydrogenolysis of racemic 3-substitued-3-hydroxyisoindolin-1-ones has been developed employing SPINOL-derived phosphoric acid and a high steric demand Hantzsch ester as the hydrogen source. The corresponding products are obtained in good yields and up to 93% enantioselectivities.     

New chiral bis(oxazoline) Rh(I)-, Ir(I)- and Ru(II)-complexes for asymmetric transfer hydrogenations of ketones

Chiral bis(oxazoline)-based Rh(I)-, Ir(I)- and Ru(II)-complexes have been prepared and used for asymmetric transfer hydrogenation of prochiral ketones. The presence of a free hydroxyl group on the ligand is necessary for high enantioselectivity. With acetophenone, up to 50% conversion and 89% ee were achieved.     

Guide to enantioselective dirhodium(II)-catalyzed cyclopropanation with aryldiazoacetates

Catalytic enantioselective methods for the generation of cyclopropanes have been of long standing pharmaceutical interest. Chiral dirhodium(II) catalysts prove to be an effective means for the generation of diverse cyclopropane libraries. Rh₂(R-DOSP)₄ is generally the most effective catalyst for asymmetric intermolecular cyclopropanation of methyl aryldiazoacetates with styrene. Rh₂(S-PTAD)₄ provides high levels of enantioinduction with ortho-substituted aryldiazoacetates. The less-established Rh₂(R-BNP)₄ plays a complementary role to Rh₂(R-DOSP)₄ and Rh₂(S-PTAD)₄ in catalyzing highly enantioselective cyclopropanation of 3-methoxy substituted aryldiazoacetates. Substitution on the styrene has only moderate influence on the asymmetric induction of the cyclopropanation.     

Tandem Rh(III)-catalyzed oxidative acylation of secondary benzamides with aldehydes and intramolecular cyclization: the direct synthesis of 3-hydroxyisoindolin-1-ones

The rhodium-catalyzed oxidative acylation between secondary benzamides and aryl aldehydes via sp(2) C-H bond activation followed by an intramolecular cyclization is described. This method results in the direct and efficient synthesis of 3-hydroxyisoindolin-1-one building blocks.     

Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxides: DIAPHOXs. Formal enantioselective synthesis of (−)-paroxetine

An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF₆, 10 mol % of LiOAc, and N,O-bis(trimethylsilyl)acetamide (BSA), affording the corresponding branched products in excellent yield and in up to 95% ee. The developed catalytic asymmetric reaction was successfully applied to a formal enantioselective synthesis of (−)-paroxetine.     

Gold(I)-catalyzed enantioselective hydroamination of N-allenyl carbamates

Treatment of the N-4,5-hexadienyl carbamate 2a with a catalytic 1:2 mixture of [(S)-1]Au2Cl2 [(S)-1 = (S)-3,5-t-Bu-4-MeO-MeOBIPHEP] and AgClO4 in m-xylene at -40 degrees C for 24 h led to isolation of 2-vinylpyrrolidine 3a in 97% yield with 81% ee. Gold(I)-catalyzed enantioselective hydroamination was effective for a number of carbamate groups and tolerated terminal disubstitutution of the allenyl moiety.     

Oxovanadium(V)-catalyzed enantioselective Meerwein-Ponndorf-Verley cyanation of aldehydes using acetone cyanohydrin

Oxovanadium(V)(salen) complex 4 was found to catalyze Meerwein-Ponndorf-Verley cyanation of aliphatic aldehydes with good to high enantioselectivity. This cyanation showed a positive nonlinear effect.     

PdCl2-catalyzed hydrogenolysis of an Ar-Cl bond by sodium phosphinate in an aqueous alkaline medium

The hydrogenolysis of the Ar-Cl bond in chlorinated benzoic acids, anilines, and nitrogen-containing heterocycles by the action of NaH₂PO₂ in the presence of catalytic amounts of PdCl₂ and NaOH in an aqueous medium was studied. Under these conditions aryl chlorides were quantitatively converted into the corresponding arenes. Chloropyridines, such as 2-chloropyridine and 3, 5-dichloropicolinic acid, did not undergo hydrogenolysis even in the presence of an equivalent amount of NaI. A distinctortho effect was observed forortho-substituted substrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 607–609, March, 1993.     

Selective hydrogenolysis of benzyl-protected 1-hydroxy-3-hydroxyimino-2-pyrrolidinones

On hydrogenolysis of 1-benzyloxy-3-benzyloxyimino-2-pyrrolidinones in the presence of 10% Pd/C selective removal occurs of the O-benzyl (Bn) protection of the hydroxamic acid, with retention of the double bond and benzyl protection of the oxime group. The yields of reaction products were 66–98%. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1011–1014, July, 2006.     

Highly enantioselective hydrogenation of new 2-functionalized quinoline derivatives

The asymmetric hydrogenation of a new series of 2-functionalized quinolines has been developed in the presence of in situ generated catalysts obtained from [Ir(cod)Cl]₂/(R)-bisphosphine/I₂ combinations. The enantioselectivity levels were as high as 84-94% ee for the synthesis of 1,2,3,4-tetrahydroquinolines.     

Novel synthesis of 3-aryl-5,6-dihydropyridin-2(1H)-ones

Cyclization of N-3-oxoalkylamides of substituted phenylacetic acids under the influence of bases produces 3-aryl-substituted 5, 6-dihydropyridin-2(1H)-ones. Dehydrogenation of these latter compounds yields substituted pyridin-2(1H)-ones.Omsk State University, Omsk 644077. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 812–815 June, 1994. Original article submitted May 6, 1994.