Scandium Triflate–Promoted Addition of Organozinc Reagents to Benzaldiminetricarbonylchromium Derivatives

The reaction of benzaldiminetricarbonylchromium derivatives with organozinc reagents in the presence of scandium triflate afforded a single diastereomer of the corresponding amine complex exclusively. Even in the case of benzaldiminetricarbonylchromium having an m‐substituent of the aromatic ring, one diastereomer was obtained using the o‐TMS‐protected chromium complex. The TMS group and the chromium moiety were easily removed and the benzyl group was deprotected using HOOH and Pd to afford the corresponding amine.     

Asymmetric Allylation of Ketones and Subsequent Tandem Reactions Catalyzed by a Novel Polymer‐Supported Titanium–BINOLate Complex

By using a novel, simple, and convenient synthetic route, enantiopure 6‐ethynyl‐BINOL (BINOL=1,1‐binaphthol) was synthesized and anchored to an azidomethylpolystyrene resin through a copper‐catalyzed alkyne–azide cycloaddition (CuAAC) reaction. The polystyrene (PS)‐supported BINOL ligand was converted into its diisopropoxytitanium derivative in situ and used as a heterogeneous catalyst in the asymmetric allylation of ketones. The catalyst showed good activity and excellent enantioselectivity, typically matching the results obtained in the corresponding homogeneous reaction. The allylation reaction mixture could be submitted to epoxidation by simple treatment with tert‐butyl hydroperoxide (TBHP), and the tandem asymmetric allylation epoxidation process led to a highly enantioenriched epoxy alcohol with two adjacent quaternary centers as a single diastereomer. A tandem asymmetric allylation/Pauson–Khand reaction was also performed, involving simple treatment of the allylation reaction mixture with Co₂(CO)₈/N‐methyl morpholine N‐oxide. This cascade process resulted in the formation of two diastereomeric tricyclic enones in high yields and enantioselectivities.     

重氮化合物与醇的插入反应合成α-烷氧基-β-二羰基化合物

研究了在过渡金属配合物催化下α-重氮-β-二羰基化合物与醇的插入反应, 考察了重氮化合物的结构、醇的结构、催化剂的性质、反应溶剂和反应温度对这一反应的影响. 发现当重氮化合物与甲醇的物质的量比为1∶10, 1 mmol% Rh₂(OAc)₄为催化剂和回流的苯的条件下, 反应能够以高的化学产率生成α-甲氧基-β-二羰基化合物. 手性醇衍生的重氮乙酰乙酸酯反应的产物中两种非对应异构体的比例为3∶2～1∶1.     

Palladium catalyzed three component coupling reaction between chromones, alcohols, and allylic acetates: diversity-oriented synthesis of highly substituted chromones

This paper describes the palladium catalyzed highly efficient three component coupling (TCC) reactions between chromones, allylic acetates, and alcohols, which lead to a library of multiply substituted chromones. The activity of various palladium catalysts, such as Pd(PPh₃)₄ and Pd₂dba₃·CHCl₃ and their combination with various bisphosphine ligands, was investigated by using THF as a solvent, which revealed that Pd(PPh₃)₄ catalyst was the best one. The reaction most probably proceeds via the formation of benzopyrilium cation, generated from the reaction between chromones and allyl acetate, in the presence of palladium catalyst. The subsequent trapping of the benzopyrilium cation by alcohols would give the corresponding products in excellent yields. This alkoxy-allylation reaction was highly diastereoselective and only one diastereomer was obtained in all the cases.     

Reactions of dialkyl 4-bromo-2,2-dimethyl-3-oxohexane-1,6-dioates,-heptane-1,7-dioates with zinc and aromatic aldehydes

Zinc enolates generated from dimethyl 4-bromo-2,2-dimethyl-3-oxohexane-1,6-dioate and zinc reacted with aromatic aldehydes giving methyl 2,2-dimethyl-3-oxo-3-(5-oxo-2-aryltetrahydrofuran-3-yl)propanoates. The reaction of zinc enolates obtained from dimethyl 4-bromo-2,2-dimethyl-3-oxoheptane-1,7-dioate and zinc with aromatic aldehydes depending on the synthesis conditions led to the formation either methyl 2,2-dimethyl-3-oxo-3-(6-oxo-2-aryltetrahydropyran-3-yl)propanoates or 3-(5,5-dimethyl-4,6-dioxo-2-aryltetrahydropyran-3-yl)propanoates. The compounds synthesized formed as a single diastereomer of E-configuration.     

New developments in the Pd-catalysed cyclisation-coupling reaction of alkene-containing carbonucleophiles with organic halides (and triflates). The first examples of asymmetric catalysis.

The results of our preliminary investigations directed toward asymmetric catalysis of the cyclocarbopalladation of alkenes bearing a proximate nucleophile with organic halides (or triflates) are disclosed. A series of bidentate phosphine ligands were evaluated in intramolecular versions of this reaction using (E)-2-[7-(2-bromophenyl)-hept-4-enyl]-malonic acid dimethyl ester (1) and (Z)-2-[7-(2-trifluoromethanesulfonyloxy-phenyl)-hept-4-enyl]-malonic acid dimethyl ester (9) as model substrates. The highest enantioselective induction was obtained with aryl triflate 9 which produced the corresponding cyclopentylindane as a single diastereomer in 54% chemical yield and 43% ee by using PdCl₂[S-(−)-TolBINAP] as chiral catalyst and K₂CO₃ as base.     

Catalytic tail-to-tail dimerization of methyl acrylate using bis(triphenylphosphine)tricarbonyl ruthenium(0)

The complex Ru(CO)₃(PPh₃)₂ catalyzes the dimerization of methyl acrylate at 120–140°C to give tail-to-tail dimers containing predominantly dimethyl (E)-2-hexene-1,6-dioate together with small amounts of trimers and polymer. The reaction under hydrogen atmosphere selectively gave tail-to-tail dimers in improved yield without formation of trimers and polymer. Under these conditions a catalyst turnover number of 246 was obtained at 130°C in 6 h.     

Iron Carbonyl Induced Reactions of Norbornene Derivatives with Substituted Acetylenes

Photochemical reactions of norbornadiene with substituted acetylenes in the presence of Fe(CO)₅ gave various products of different types, depending on the nature of the acetylene. The results are summarized in Table 1. The cyclopentanone 1 was always formed in these reactions. In the reaction of disubstituted acetylenes such as dimethyl acetylenedicarboxylate and ethyl phenylpropiolate, the cyclopentenones 2 and 5 were formed, respectively. By contrast, propiolic esters produced the cyclohexenones 3 and 4 , in which the ester group was attached on the β carbon with respect to the keto group. Plausible mechanisms for the formation of these products are shown in Schemes 7 and 8. The reaction of diphenylacetylene gave the cyclohexendione 7 as well as the cyclopentenone 6 . Two enedione products 8 and 9 were obtained from the reaction of phenylacetylene. Compound 9 was converted to the aromatic diacetate 13 by heating with acetic anhydride in pyridine. On irradiation in the presence of Fe(CO)₅ norbornene reacted similarly with dimethyl acetylenedicarboxylate and phenylacetylene to give the cyclopentenone 14 and the cyclohexenone 15 , respectively. Compound 15 , upon heating, isomerized to hydroquinone 16 , which on acetylation gave the diacetate 17 .     

gem‐Dimethylcyclopropanation of dibenzylideneacetone using triisopropyl sulfoxonium tetrafluoroborate

The reaction between dibenzylideneacetone (dba) and triisopropyl sulfoxonium tetrafluoroborate has been reinvestigated. The stereochemistry of the major diasteromeric bis(gem‐dimethylcyclopropane) adduct has now been assigned as [(1RS,3RS)‐2,2‐dimethyl‐3‐phenylcyclopropyl][(1SR,3SR)‐2,2‐dimethyl‐3‐phenylcyclopropyl]methanone, C₂₃H₂₆O, by X‐ray crystallographic studies on a twinned crystal. The asymmetric unit contains two molecules of the adduct, the conformations of which differ in the orientation of the phenyl ring relative to the adjacent cyclopropanated double bond. The carbonyl groups of each adduct are aligned approximately along the a axis and in opposite directions to each other. The molecules pack to give a sinusoidal pattern along the b axis. This is the first acyclic bis(dimethylcyclopropyl) ketone for which an X‐ray crystal structure determination has been reported, and is also the first bis‐cyclopropanated dba analogue. The knowledge that the major diastereomer has the meso structure (and therefore the confirmation that the minor isomer is the racemate) will prove invaluable in future studies to utilize bis(dimethylcyclopropyl) ketones as reagents, in rearrangement processes, and as potential ligands and ligand precursors in organometallic chemistry.     

2‐Chloro‐3‐(dimethylamino)prop‐2‐enoyl Fluoride,a Stable Acyl Fluoride

The title compound is formed as a side‐product in the reaction of CF₃CCl₃ with Zn/DMF and dimethyl(thexyl)silyl chloride (=dimethyl(1,1,2‐trimethylpropyl)silyl chloride). The structure and the double‐bond configuration are deduced from its ¹³C‐NMR data. Its formation is discussed in terms of a Vilsmeier‐type formylation and a reductive elimination.     

A New Strategy for the Synthesis of Polytrithiocarbonates Using a Polymeric Support System

A new polymerization strategy, consisting of nucleophilic substitution reaction between CS₃^2‐, immobilized on a polymeric support, and dimethyl α,α′‐dibromoalkylanedioate in solution, leads to the formation of polytrithiocarbonates. When n = 0, 1 in CH₃OOCCHBr(CH₂)_nCHBrCOOCH₃ (α,α′‐dibromoalkylanedioate), only five‐ or six‐membered cyclic trithiocarbonates were obtained; n ≥ 2 resulted in the formation of polytrithiocarbonates.     

Synthesis and Chiroptical Properties of Dimethyl 8,12-Diphenylbenzo[d]heptalene-6,7-dicarboxylate

6,10-Diphenylbenz[a]azulene ( 3 ) was reacted with dimethyl acetylenedicarboxylate (ADM) in the presence of 2 mol-% of [RuH₂(PPh₃)₄] in MeCN at 100° to yield a 7:1 mixture of dimethyl 2,6-diphenyl-9,10-benzotricyclo[6.2.2.0^1,7]dodeca-2,4,6,9,11-pentaene-11,12-dicarboxylate ( 4 ) and dimethyl 8,12-diphenylbenzo[d]heptalene-6,7-dicarboxylate ( 5 ; Scheme 2). The tricycle 4 , when heated in DMF at 150° for 1 h led to the formation of 81.5% of the heptalene-6,7-dicarboxylate 5 and 15% of the starting azulene 3 . No rearrangement of tricycle 4 was observed, when it was heated at temperatures up to 180° in pseudocumene. The heptalene-6,7-dicarboxylate 5 was easily separated into its antipodes (PM)-and (MP)- 5 on a Chiracel column (cf. Fig. 2). On heating at 150° for 1 h, (MP)- 5 showed no racemization at all. The Ru-catalyzed reaction of benz[a]azulene ( 6 ) with ADM led to the formation of dimethyl 9,10-benzotricyclo[6.2.2.0^1,7]dodeca-2,4,6,9,11-pentaene-11,12-dicarboxylate ( 7 ; Scheme 3). However, the formation of the corresponding heptalene-6,7-dicarboxylate could not be observed.     

Synthesis of laddersiloxanes by novel stereocontrolled approach

Three new pentacyclic laddersiloxanes were prepared by a new method utilizing single stereoisomer of disiloxanediol as a growing unit. Thus, one diastereomer of disiloxanediol, (RS)–[i-PrPhSi(OH)]₂O was isolated and treated with tetrachlorocyclotetrasiloxane, resulting in the formation of tricyclic laddersiloxanes with cis-Ph groups at terminals. All of the obtained isomers could be transformed into pentacyclic laddersiloxanes by dephenylchlorination followed by the reaction with (RS)–[i-PrPhSi(OH)]₂O. The structures of new tricyclic and pentacyclic laddersiloxanes were determined by X-ray crystallography. The thermogravity properties of laddersiloxanes depending on the molecular weight and structures were summarized.     

Kinetics and reactivity of substituted anilines with 2‐chloro‐5‐nitropyridine in dimethyl sulfoxide and dimethyl formamide

The kinetics of the reaction of substituted anilines with 2‐chloro‐5‐nitropyridine were studied in dimethyl sulfonide (DMSO) and dimethyl formamide (DMF) at different amine concentrations and temperatures in the range 45–60°C. In both solvents the reaction was not a base‐catalyzed one. A plot of ΔH^# versus ΔS^# for the reaction in DMSO and DMF gave good straight lines with isokinetic temperatures 128°C and 105°C, respectively. Good linear relationships were obtained from the plots of log k₁ against σ° values at all temperatures with negative ρ values (?1.63 to ?1.28 in DMSO) and (?1.26 to ?0.90 in DMF). © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 645–650, 2002     

Thermal Reaction of Azulenes with Dimethyl Acetylenedicarboxylate in Supercritical Carbon Dioxide

1,3,4,6,8-Pentamethylazulene ( 9 ), when heated at 100° in supercritical CO₂ at 150 bar in the presence of 4 equiv. of dimethyl acetylenedicarboxylate (ADM), led to the formation of 16% of a 1:1 mixture of dimethyl 3,5,6,8,10-pentamethylheptalene-1,2-dicarboxylate 12a ) and its double-bond-shifted isomer 12b as well as 4% of the corresponding azulene-1,2-dicarboxylate 13 (Scheme 4). The formation of the [1 + 2] adduct 11 (cf. Scheme 2) was not observed. Similarly, benz[a]azulene ( 25 ) yielded in supercritical CO₂ (150°/170 bar) in the presence of 4 equiv. of ADM dimethyl benzo[d]heptalene-6,7-dicarboxylate ( 29 ; 30%) and dimethyl benzo[a]cyclopent[cd]azulene-1,2-dicarboxylate ( 28 ; 22%; Scheme 5). The reaction of 5,9-diphenylbenz[a]azulene ( 26 ) and ADM in supercritical CO₂ (100°/150 bar) gave the corresponding benzo[d]heptalene-6,7-dicarboxylate 31 (22%) and dimethyl 5,9-diphenyl-4b,10-etheno-10H-benz[a]azulene-11,12-dicarboxylate( 30 ; 25%; Scheme 5).     

Synthesis and some transformations of dimethyl anabasylethynephosphonate

A new phosphorylated ynamine, dimethyl anabasylethynephosphonate, was synthesized by reaction of dimethyl chloroacetylenephosphonate with anabasine. Anabasylethynephosphonate obtained was shown to react under mild conditions with primary aromatic amines like p-chloroaniline, p-anisidine, and p-aminoacetophenone, whose pK _b values are in the range of 9–13, to form new asymmetrical phosphorylated acetamidines in high yields. Structure of the compounds obtained was proved by ¹H, ¹³C, and ³¹P NMR spectroscopy.     

Electrophilic substitution reactions of indole alkaloids with α,β-unsaturated carbonyl compounds in the presence of K10 montmorillonite

Reactions of indole, 1-methylindole, and 3-methylindole with dimethyl acetylenedicarboxylate in the presence of K10 montmorillonite as a catalyst led to the formation of the corresponding dimethyl 2,2-bis(indolyl)butanedioates. The reaction of 2-methylindole with dimethyl acetylenedicarboxylate gave dimethyl 2-(2-methyl-1H-indol-3-yl)maleate and dimethyl 2-methyl-1H-1-benzoazepine-3,4-dicarboxylate. Dimethyl 1,5-dimethyl-1H-1-benzoazepine-3,4-dicarboxylate was obtained by treatment of 1,3-dimethylindole with dimethyl acetylenedicarboxylate using K10 clay as a catalyst. Published in Russian in Zhurnal Organicheskoi Khimii, 2006, Vol. 42, No. 6, pp. 900–902. The text was submitted by the authors in English.     

Kinetic Model of the Reaction of Methanol with Hydrogen Sulfide

The kinetics of the reaction of methanol with hydrogen sulfide in the presence of an IKT-31 catalyst was experimentally studied. The experiments were performed in a fixed-bed flow reactor under the following conditions: T = 598-653 K, P = 0.1-1.0 MPa, and P⁰ _{H 2 S}/P⁰ _Me =0.4-15.0. Rate equations were derived which describe the rates of formation of methanethiol as the main product and dimethyl sulfide and dimethyl ether as by-products. The rate constants and activation energies were found by the mathematical treatment of experimental data. The model proposed can be used for reactor design.     

Synthesis and characterization of ruthenium(ii) complexes of 5-hydroxyflavones

Bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complexes, RuL₂(DMSO)₂, were synthesized by the reaction of dichlorotetrakis(dimethyl sulfoxide)ruthenium(II) with the sodium salts of 5-hydroxyflavone, 5-hydroxy-4′-methoxyflavone and 5-hydroxy-3′,4′,5′,7-tetramethoxyflavone, ( L ). The complexation was followed by ¹H nmr spectroscopy. The 1:1 kinetically favoured tris(dimethyl sulfoxide)chloroflavonatoruthenium(II) complexes, RuLCl(DMSO)₃, were initially formed and then transformed into the thermodynamically more stable ones. Each one of these complexes, by reacting with another equivalent of lig-and L, also gave rise to a mixture of 1:2 kinetic species, from which the 1:2 thermodynamically more stable bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complexes, RuL₂(DMSO)₂, were formed. The complexes were characterized by extensive studies involving ¹H, ¹³C nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopy, mass spectrometry, cyclic voltammetry and elemental analysis. Such 1:2 complexes exhibited properties of two nonequivalent flavonate ligands and also of two non-equivalent dimethyl sulfoxide ligands; one of these dimethyl sulfoxide ligands is considered to be S-bonded and the other O-bonded. Also two quasireversible one-electron redox steps were observed at 0.53 to 0.57 and 0.44 to 0.41 V (vs Saturated Calomel Electrode). The spectroscopic results obtained allow for the discussion of stereochemistry of each bis(dimethyl sulfoxide)bis(flavonato)ruthenium(II) complex and to postulate its possible structure as one corresponding to the more anisochronous species.     

Synthesis,Crystal Structure,and Diastereomeric Transfer of Pentacoordinated Phosphoranes Containing Valine or Iso-Leucine Residue

Pentacoordinated phosphoranes containing valine or iso-leucine residue (2-phenyl-2,7⁵-spiro[1,3,2-phenanthrodioxaphosphole-2,2′-1,3,2-oxazaphospholan]-5′-one) were synthesized through sequential two-step reactions, whereby the reaction products of phenyldichlorophosphine with N,O-bis(trimethylsilyl)valine or iso-leucine were followed by the addition of phenanthrenequione, and the crystals of 4a and 4b were obtained from benzene and hexane mixed solution. The x-ray structure of the crystals 4a and 4b revealed that they are distorted TBP, exhibiting R_P absolute configuration. The ³¹P NMR spectra showed that the S_P diastereomer could transfer into the other one R_P that came out from the solution during crystallization. Correspondingly, when it was dissolved in solvents the R_P diastereomer transferred into the other one S_P, and the pair of diastereomers changed each other in solution at room temperature through a phosphonium carboxylate zwitterions intermediate.