Novel synthesis of enantiomerically pure natural inositols and their diastereomers

A novel synthesis of all stereoisomers of natural inositols has been developed. The key strategy is the stereoselective reduction of substituted β-hydroxy cyclohexanones, which are prepared from a variety of 6-O-acetyl 5-enopyranosides via Ferrier-II reaction catalyzed by palladium chloride. The utility of this approach is demonstrated by the synthesis of D-myo-inositol 1,4,5-tris(phosphate)(IP₃).     

Synthesis of enantiomerically pure Sb-chirogenic organoantimony compounds and their crystal structures

Sb-chirogenic organoantimony compounds (±)-5a-c bearing heteroatom moieties such as 4,4-dimethyl-2-oxazolinyl, methoxymethyl, and diphenylphosphanyl substituents on the o-position of an aryl group have been prepared by nucleophilic displacement of the ethynyl moiety on (1-naphthyl)(phenylethynyl)(p-tolyl)stibane (3) with aryllithium reagents (2a-c). The optical resolution of the racemic (±)-5a,b was attained via separation of a diastereomeric mixture of their palladium complexes (S)-7 formed from the reactions of (±)-5a,b with di-μ-chlorobis[(S)-dimethyl(1-ethyl-α-naphthyl)aminato-C²,N]dipalladium(II) (6). The enantiomerically pure Sb-chirogenic stibanes isolated here were optically stable, and no racemization on the chiral antimony center was observed even when they were allowed to stand at room temperature for over 72 h in chloroform. The structure of 5a,b including the absolute configuration was determined by single crystal X-ray analyses of (+)-5aB and antimony-palladium complex (7bB), respectively. The analyses also revealed the presence of intramolecular interaction between the antimony and sp²-nitrogen atoms in the molecule Sb(S)-(+)-5aB.     

Reactions of organic halides with organometallic compounds and terminal acetylenes catalyzed by palladium complexes

The results of the investigation of the cross-coupling of organometallic compounds and terminal acetylenes with organic halides catalyzed by transition metal complexes are generalized and analyzed. The influence of different factors on the rate and selectivity of catalytic cross-coupling is discussed. A detailed mechanism of the cross-coupling of Grignard reagents with organic halides is suggested. The cross-coupling reaction involving organotin compounds proceeds under very mild conditions in the presence of a ligand-free Pd catalyst. Examples of using catalytic cross-coupling of organic halides with organomagnesium, organozinc, and organotin compounds are presented.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2148–2167, September, 1996.     

Regioselective diarylation of ketone enolates by homogeneous and heterogeneous catalysis: synthesis of triarylethanones

A novel, one-step approach to 1,2,2-triarylethanones is achieved by an efficient palladium-catalyzed α,α-diarylation of commercially available acetophenones. After assaying an array of experimental conditions, two convenient procedures, which avoid ortho-arylation side reactions, are chosen to perform the target regioselective diarylation. The former protocol is based on the use of such a simple homogeneous system as Pd(OAc)₂/PPh₃/Cs₂CO₃, and the latter one employs a commercially available polymer-anchored catalyst, FibreCat™ 1026.     

Effective heterogeneous palladium catalysis of the reactions of organoboron compounds with aryl halides

Reactions of [Ph₄B]Na and ArB(OH)₂ with aryl halides are effectively catalyzed by heterogeneous palladium catalysts (PdCl₂C, Pd(0)/C, and palladium black) to give cross-coupling products in high yields. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1399–1401, July, 1997.     

Electrosynthesis of arylalkanoic acids by oxidation of the corresponding arylalkanols at the Ni anode in aqueous alkali

The electrochemical synthesis of a series of aryl(aryloxy)alkanoic acids was carried out by the electrocatalytic oxidation of the corresponding alcohols with the general formula RCH₂CH₂OH (R = Ar, CH₂Ph, OPh) in an undivided cell at the NiOOH electrode in aqueous alkali. The efficiency of the process depends on the structure of the starting alcohols, particularly, on the donor-acceptor properties of the substituent R. These properties determine the possibility of the primarily formed RCH₂COO⁻ anion to be oxidized forming by-products. The yield of the target acids upon the oxidation of 2-(2-hydroxyethyl)pyridine, 2-phenylethanol, 3-phenylpronan-1-ol, and 2-phenoxyethanol was 15, 53, 75, and 93%, respectively, based on the reacted alcohol. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 481–485, March, 2007.     

Triethylborane as an efficient promoter for palladium-catalyzed allylation of active methylene compounds with allyl alcohols

Without prior activation of allyl alcohols, allylation of a variety of active methylene compounds with allyl alcohols proceeds smoothly at rt-50°C in the presence of catalytic amounts of Pd(OAc)₂ (1-10 mol%), Et₃B (30-240 mol%), a phosphine ligand (1-20 mol%), and a base (0 to 50-60 mol%).     

Cross-coupling of polychloroarenes with phenylboronic acid and organozinc compounds catalyzed by palladium complexes

Hexachlorobenzene and 1,2,4,5-tetrachlorobenzene react with phenylboronic acid by a C—C cross-coupling mechanism with a Pd(dba)₂/P(Bu^t)₃ system (dba is dibenzylideneacetone) or palladium-azole complexes as catalysts, or with organozinc compounds in the presence of Pd(PPh₃)₄ to afford substitution products of one or two chlorine atoms in moderate yields. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 947–951, April, 2005.     

Selective reduction of alkynes catalyzed by palladium acetate with sodium methoxide as the hydride source

Treatment of internal alkynes with sodium methoxide in the presence of Pd(OAc)₂ and PPh₃ in methanol for 48 h gave the reduction products, alkenes or alkanes in good chemical yields. This reaction proceeds through a palladium methanolate complex, followed by β-hydride elimination and reductive elimination.     

A simple and efficient hydrogenation of benzyl alcohols to methylene compounds using triethylsilane and a palladium catalyst

Hydrogenolysis of benzyl alcohols using triethylsilane (Et₃SiH) and a catalytic amount of palladium(II) chloride (PdCl₂) is described. The reaction takes place under mild conditions affording high yields of the corresponding methylene compounds in short reaction times.     

Kinetic Resolution of Racemic Allylic Alcohols by Catalytic Asymmetric Substitution of the OH Group with Monosubstituted Hydrazines

A new strategy has been established for the kinetic resolution of racemic allylic alcohols through a palladium/sulfonyl‐hydrazide‐catalyzed asymmetric OH‐substitution under mild conditions. In the presence of 1 mol % [Pd(allyl)Cl]₂, 4 mol % (S)‐SegPhos, and 10 mol % 2,5‐dichlorobenzenesulfonyl hydrazide, a range of racemic allylic alcohols were smoothly resolved with selectivity factors of more than 400 through an asymmetric allylic alkylation of monosubstituted hydrazines under air at room temperature. Importantly, this kinetic resolution process provided various allylic alcohols and allylic hydrazine derivatives with high enantiopurity.     

Direct and Selective Synthesis of Adipic and Other Dicarboxylic Acids by Palladium-Catalyzed Carbonylation of Allylic Alcohols

A general and direct synthesis of dicarboxylic acids including industrially important adipic acid by palladium-catalyzed dicarbonylation of allylic alcohol is reported. Specifically, the combination of PdCl₂ and a bisphosphine ligand (HeMaRaphos) promotes two different carbonylation reactions with high activity and excellent selectivity.     

A new synthetic entry to the tricyclic skeleton of FR901483 by palladium-catalyzed cyclization of vinyl bromides with ketone enolates

A new synthetic entry to the FR901483 core is described. The Pd-mediated cyclization of amino-tethered vinyl halides and ketone enolates from the azaspiro[4.5]decan-8-ones 5 and 10 gives the functionalized 7,10a-methanoperhydropyrrolo[1,2-a]azocines 1 and 11, respectively.     

Cooperative Catalysis by Palladium and a Chiral Phosphoric Acid: Enantioselective Amination of Racemic Allylic Alcohols

Cooperative catalysis by [Pd(dba)₂] and the chiral phosphoric acid BA1 in combination with the phosphoramidite ligand L8 enabled the efficient enantioselective amination of racemic allylic alcohols with a variety of functionalized amines. This catalytic protocol is highly regio‐ and stereoselective (up to e.r. 96:4) and furnishes valuable chiral amines in almost quantitative yield.     

Efficient and selective oxidation of alcohols in water employing palladium supported nanomagnetic Fe3O4@hyperbranched polyethylenimine (Fe3O4@HPEI.Pd) as a new organic–inorganic hybrid nanocatalyst

Palladium immobilized magnetic nanoFe₃O₄@hyperbranched polyethylenimine (Fe₃O₄@HPEI.Pd) was prepared according to a simple and cost effective pathway and it was employed as a new efficient and selective organic–inorganic hybrid nanocatalyst for the aqueous oxidation of primary and secondary alcohols to their corresponding products in good yields applying oxone (potassium hydrogen monopersulfate) and H₂O₂ as an oxidant at room temperature. Moreover, the catalytic system was reused at least 13 times without significant loss of activity. The complete characterization of this efficient nanocatalyst was investigated by FTIR, UV–Vis, TEM, SEM, XRD, TGA, VSM, ICP and EDX techniques.     

Highly selective, recyclable epoxidation of allylic alcohols with hydrogen peroxide in water catalyzed by dinuclear peroxotungstate

The highly chemo-, regio-, and diastereoselective and stereospecific epoxidation of various allylic alcohols with only one equivalent of hydrogen peroxide in water can be efficiently catalyzed by the dinuclear peroxotungstate, K2[[W(=O)(O2)2(H2O)]2(mu-O)].2H2O (I). The catalyst is easily recycled while maintaining its catalytic performance. The catalytic reaction mechanism including the exchange of the water ligand to form the tungsten-alcoholate species followed by the insertion of oxygen to the carbon-carbon double bond, and the regeneration of the dinuclear peroxotungstate with hydrogen peroxide is proposed. The reaction rate shows first-order dependence on the concentrations of allylic alcohol and dinuclear peroxotungstate and zero-order dependence on the concentration of hydrogen peroxide. These results, the kinetic data, the comparison of the catalytic rates with those for the stoichiometric reactions, and kinetic isotope effects indicate that the oxygen transfer from a dinuclear peroxotungstate to the double bond is the rate-limiting step for terminal allylic alcohols such as 2-propen-1-ol (1a).     

Cobalt(II), nickel(II) and copper(II) compounds derived from template reactions of enantiomerically pure 2-amino-thiazoles

Herein we report the syntheses and structural analyses of three coordination compounds Co(L)₂ (3), Ni(L)₂, (4) and Cu(L)₂ (5) (L = bis[(4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl]-amine) prepared by template reactions from the optically active ligand (4R,5R)-4-methyl-5-phenyl-4,5-dihydro-thiazol-2-yl-amine (1) and CoCl₂·6H₂O, NiBr₂·3H₂O or Cu(OAc)₂·H₂O The template reactions involve the condensation of two molecules of thiazol-2-yl-amine and elimination of one NH₃. The resulting bidentate ligand coordinates to the metal ion through the imine nitrogen atoms forming a six-membered ring, presenting an electronic delocalization which averages the four M–N bond lengths. The distorted tetrahedral geometry of the metal atoms gives place to complex electronic spectra for compounds 3–5. A mixed ionic compound (6) formed by three cations (4S,5S)-3,4-dimethyl-5-phenyl-thiazolidin-2-ylidene ammonium, one dianion tris-(thiocyano)bromide cobaltate and one bromide, obtained from reaction of (4S,5S)-3,4-dimethyl-5-phenyl-thiazolidin-2-ylidene ammonium thiocyanate (2) and CoBr₂ is also described. Compounds 3–6 were characterized in the solid state by UV–Vis–NIR and IR spectroscopy, mass spectrometry and X-ray diffraction analyses. Metal···H–C, S···H–C interactions were observed in 3–6, whereas in 6, also Br···H–N, Br···H–C and Br···S, S···S short contacts were found.