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The cyclopentadienyl-free simple lanthanide amides are shown are highly efficient catalysts for the guanylation of both aromatic and secondary amines with a high activity under mild conditions. The results have shown that these catalysts are compatible with a wide range of solvents and substrates.

Study of usage of Calcium ionic waves as catalysts of starfish oocytes with sperm is presented.

Diaryl hydrazides prepared from the Pd(0)- or Cu(I)-catalyzed coupling reactions of aryl hydrazides and aryl halides underwent the acid-catalyzed rearrangements to a series of previously unknown 2,2'-diaminobiaryls in good overall yields. The mildness of the reaction conditions allows the presence of various functional groups.

The reaction of 4, 6-O-benzylidene-D-pyranosides with a stoichiometric amount of TsCl, AcCl, and BzCl in the presence of silver(I) oxide and a catalytic amount of potassium iodide led to monosubstituted derivatives in high regioselectivity and in good yields.

The Ru(sub3)(CO)(sub 12)-catalyzed decarbonylative reduction of esters with ammonium formate (HCOONH(sub 4)) leading to hydrocarbons is also described. The key step for both catalytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.

The functional roles for His44, His47, Asn69, Gln72, Lys160 and Gln164 residues in the binding of substrates and the pantoyl adenylate intermediate are evaluated by constructing six Ala mutants and determining their catalytic properties. The results indicate that the highly conserved His44, His47, Asn69, Gln72, Lys160 and residues are necessary for the formation and stabilization of pantoyl adenylate intermediate in the pantothenate synthetase reaction.

Catalyzed asymmetric aryl and alkyl transfer reactions onto aldehydes are enhanced by the addition of small amounts of simple methoxy poly(ethyleneglycol)s (MPEGs). The enantiomeric excesses of the products improve by the process and the catalyst loading reduces by a factor of 10.

A set of analogues and dipeptide amides characterized by chiral C(super alpha)-tetrasubstituted alpha-amino acids of varied bulkiness and optical configurations are examined. Results confirm the close relationship between the beta-hairpin 3D-structure and the catalytic activity of the peptides.

An efficient trifluoacetone (CF3COCH3)-catalyzed epoxidation using a hydrogen peroxide (H2O2) as primary oxidant at high pH, is reported. The usage of H2O2 as oxidant significantly reduces the amount of the solvent and salt introduced.

Several substituted 2-pyrones were hydrogenated with high enantioselectivity to the corresponding 5,6-dihydropyrones utilizing cationic ruthenium catalysts containing the (6,6'-dimethoxybiphenyl-2,2'diyl)bis(3,5-di(tert-butyl)phenylphosphine) ligand. When substituents at position are absent, 5,6-dihydropyrones were further hydrogenated to the fully saturated delta-lactones. For the case of 4,6-dimethyl-2H-pyran-2-one, the diastereoselectivity of the second hydrogenation step was determined by the chirality of the employed catalyst, while for the 4,5,6-trimethyl-2H-pyran-2-one a double asymmetric induction effect was seen.

Research was conducted to examine the cross-metathesis reactions of allyl alpha-D-galactopyranoside derivative with a number of olefins using Grubb's ruthenium benzylidene catalyst. Terminal alkenes having a wide range of protecting groups were employed as cross-metathetic partners to permit syntheses of glycosides with extended spacers and functionality in the aglycon moieties. Transstereoselectivity was observed to be good to excellent in almost all cases.

A three-step synthesis of N-acylated derivatives of N-acetylneuraminic acid (Neu5Ac) was developed based on the selective reactivity of indium toward allylic halides and its inability to reduce the aldehyde function. The synthetic process relies on the indium-mediated allylation of unprotected carbohydrates in aqueous ethanol which proceeds in a manner that is similar to the (chemo)enzymatic syntheses of sialic acids. Furthermore, the method can be utilized for the introduction of amino acids, fluorescent tags or (photo)affinity labels to the C-5 position of neuraminic acid.

GENERAL INTRODUCTION Although fermentation dates the use of biocatalytic transformations as centuries old, it has only been in recent decades that chemists have begun to rationally exploit the synthetic potential [...]

An enantioselective synthetic route for obtaining (+)- boronolide employs the Sharpless catalytic asymmetric dihydroxylation of (E)-1-(tert-butyldimethylsiloxy)-7-dodecen-5-yne, followed by Lindlar reduction of the triple bond of diacetate. Diastereoselective dihydroxylation of the resulting cis-olefin gives (+)- boronolide in high essentially enantiomerically pure and chemical yield. This technique for obtaining physiologically active natural lactonic compounds may also be applied for the synthesis of other stereoisomers of boronolide.

The hydrostannation of acetylenes by tributyltin hydride, catalyzed by Lewis acids such as ZrCl4 or HfCl4, produces cis vinylstannanes. The reaction involves regio- and stereoselective anti-hydrostannation. The hydrostannation by dibutyltin dihydride produces stereodefined Z-Z divinyltin derivatives. The reaction process occurs via an anti-hydrostannation pathway. High stereoselectivity and chemical yield require the use of nonpolar solvents, such as toluene or hexane, and temperature maintenance at 0 degree celsius.

The efficient aerobic oxidation of cycloalkanes and alkylbenzenes is possible under mild conditions with the use of a catalytic system involving N-Hydroxyphthalimide (NHPI) and Co(acac)(sub n) (n = 2 or 3). The presence of small amounts of Co(acac)(sub n) significantly enhances the catalytic activity of NHPI. The oxidation of cycloalkanes with molecular oxygen in the presence of a catalytic amount of NHPI and Co(acac)(sub 2) in acetic acid at 100 degrees celsius is discussed.

The yields of mono- and di-alkylated amines vary with the type of ruthenium complexes used as catalysts during the N-alkylation of heteroaromatic amines with alcohols. 2-aminopyridine reacts with excess of ethanol at 180 degrees celsius for 20 hours to give 9% 2-(ethylamino)pyridine (1) and 70% 2-(diethylamino)pyridine with dichlorotris(triphenylphosphine)ruthenium as catalyst. The use of (eta(super 4)-1,5-cyclooctadiene)(eta(super 6)-1,3,5-cyclooctatriene)ruthenium as catalyst forms 85% of 1 even in excess of ethanol. The use of tertiary phosphines and phosphites increases the dialkylated form.

The imino proton exchange from the close terminal base pair of a DNA duplex is a very slow process and the exchange cannot occur through a base pair with one face completely exposed to the solution. The complementary base provides protection from proton exchange due to the involvement of proton in a hydrogen bond or to the obstruction of favourable direction of attack by the exchange catalysts. The theoretical estimate of the protection factor is yet to be calculated.

The acid-catalyzed rearrangement of 2,6-dimethoxycinnamic acid ethyl ester 3 to calix(4)resorcinarenes is presented. These arenes are the same as those obtained from the 2,4-dimethoxy isomer. The values obtained through 1H NMR spectrum and molecular mechanics calculations substantiated the experimental results.

The MnO2-catalyzed hydrogen atom transfer addition of ketones to various allyl- and vinylsilanes is an innovative, cost efficient and versatile technique.High yields, 59-75%, of gamma and delta-silyl ketones are produced from common materials. The carbon-carbon bond formation is promoted by a silicon atom's alpha- and beta-electronic effects with the silyl group's steric effect producing the regioselectivity.

Reaction of boroxines with o-bis(bromomethyl)arenes, catalyzed by palladium, in the presence of 2 M sodium carbonate yields dihydro(2,3,-bis) furans and furan-3,4,-diyl dimers. The incorporation of trimethylsilyl groups in the oligomers enables the introduction of a variety of substituents. Symmetrical and unsymmetrical furan-3,4-diyl dimers, trimers and tetramers are also synthesized using this technique.

Nearly 40% overall yield of huperzine A results from a palladium-catalyzed bicycloannulation pathways to this alkaloid which was isolated from Huperzia serrata, a Chinese club moss. This approach was used with seven other huperzine A analogues and their antilcholinesterase activity in the inhibitor of rat cortex acetylcholinesterase (AChE) was examined. All of them were less effective as AChE inhibitors than the parent structure.

2,4-dimethylphenol, 2,5-dimethylphenol, 2,4-dimethylanisole, 4-methylbenzyl alcohol and tiny quantities of 2,5-dimethylanisole and 4-methylbenzyl methyl ether, result from the specific acid-catalyzed hydrolysis of 3,6-dimethoxy-3,6-dimethyl-1,4-cyclohexadiene in 25 vol % acetonitrile in water at 25 degrees centigrade. Reaction to benzylic products involves a rate restricting role of the dehydronation of the cyclohexadienyl carbocation.

Nickel-catalyzed electroreductive carboxylation on conjugated and nonconjugated diynes is discussed. Electrosynthesis was carried out using single-compartment cells fitted with a magnesium anode and air-stable Ni(II) as catalyst precursor. Ni(II) complexes included Ni(bpy)3(BF4)2 or NiBr2.DME (DME = dimethoxyethane) associated with phosphines or basic polyamines. Main reaction products included unsaturated monocarboxylic acids. Regio- and stereoselectivity were affected by diyne structure and catalytic system used.

The nickel-catalyzed reactions of iodofluoroacetates (ICF2CO2R) with alkenes and zinc in tetrahydrofuran produce alpha,alpha-difluoro esters in 60-83% yields. In the case of dienes, the product depends on the chain length and the alkene/haloester ratio. With 1, 8-nonadiene and 1,5-hexadiene, two equivalents of ICF2CO2Et produce alpha, alpha,omeega,omega-tetrafluoro esters. With 1,6-heptadiene, 1/2 equivalent of ICF2CO2Et gives a mix of ethyl 2,2-difluoro-8-nonenoate and a cylopentyl-substituted alpha,alpha-difluoro ester. The inhibiting action of p-nitrobenzene and hydroquinone on the reactions supports a one-electron transfer mechanism.

A practical and convenient route to alpha,alpha-difluorophosphonates involves the palladium-catalyzed addition of diethyl iododifluoromethylphosphonate to alkenes. With dienes, biterminal tertrafluoroalkylene bisphosphonates instead of 1,1-difluoro-3-iodoalkylphosphonates are produced. Copper may also replace palladium, but the reactions are slower. The reaction conditions tolerate a number of other functional groups in the substrates. However, reaction with diallyl ether yields a cyclization product instead. When the adducts are treated with zinc in moist tetrahydrofuran in the presence of nickle chloride, the corresponding alpha,alpha-difluorophosphonates are formed.

The cyclocondensation of electron-rich dienes with racemic alpha- and beta- thio-substituted aldehydes allows a stereochemical study of this process. Generally, the alpha- and beta-thio stereocenters provide good to excellent levels of stereocontrol, in complementation with the steric structure of the aldehydes. Among the Lewis acids (LAs) used as catalysts, etheric boron trifluoride proves the most effective in terms of the pyranone product yields (54-74%) and diasteroemeric ratios (up to 98:2) obtained. Other LAs give lower yields and a few even reverse the diastereomeric bias. Other aspects of the stereochemistry are also discussed.

The Red-Al/CuBr/2-butanol mix in tetrahydrofuran reduces the 1,4-olefinic bond of enones close to butadiene tricarbonyl iron complexes. This allows the syntheses of the 6,7-dihydro methyl ester, the 5-epi analogue and the 5-oxo derivative of leukotriene B4 (LTB4). The natural versions of the three are suspected metabolites of this potent chemotactic agent. The synthetic process require the use of Fe(CO)3 as a protecting block to enable the regioselective reduction of the alpha-double bond. Decomplexation is achieved by the use of ceric ammonium nitrate in methanol.

The use of copper in the phase transfer catalyzed (PTC) allylation of alkynes allows the use of inexpensive low polarity solvents. In a biphasic system consisting of alkali and dichloromethane (CH2Cl2) and benzyltriethylammonium chloride as PT catalyst, copper(I) chloride provides the interphase transport mechanism that enables the reaction of aryl- and alkylacetylenes with allylic bromides. The yield is 50-93%. The mechanism involves solubilization in CH2Cl2 of otherwise insoluble CuCl by interaction with the lipophilic quaternary ammonium cation.

A study of the nickel-catalyzed reactions of benzylic thioethers with Grignard reagents sheds light on the role of the omega-heteroatom and of other structures on the C-S bond's reactivity. Thioethers with beta-hydrogens form an intermediate that undergoes beta elimination to yield an olefin (styrene). For the C-S bond to be activated, the leaving group must be able to yield an anion that can coordinate to the nickel to form the intermediate. The length of the chain connecting the heteroatom to the sulfur atom and the size of the aryl group offer steric hindrance to formation of the complex. A related reaction is also discussed.

Second-order asymmetric transformation of racemic binaphthol provides the optically pure (-) enantiomer while stepwise Cu(II)-mediated coupling followed by kinetic crystallization yields the enantiomerically pure (+)- and (-)-2,2'-diamino- and the (+)- and (-)-2-amino-2-hydroxy-1,1'-binapthyls. The chemical yields for the five enantiomers are 36%, 13%, 22%, 23% and 24% respectively. The first enantiomer can also be prepared in 100% optical purity and 14% yield by coupling the copper complex of (-)-sparteine with 2-naphthol. Besides inexpensively providing these chiral ligands, the new techniques promise to find wide application in the preparation of other enantiomerically pure compounds.

The use of the silyl function allows three ways to start Michael reactions. Selective inter- and intramolecular additions are done through fluoride- or m-chlorobenzoate-catalyzed reaction of unsaturated diesters with silyl ketene acetals. Mild Lewis acids like ZnI2 catalyze less selective additions but still allow enough stereocontrol and a wider choice of silyl ketene acetals. Stronger Lewis acids like SnCl2/TiCl4 are useful in both silyl ketene acetal and silyl enol-initiated reactions with bis enones, the products of which can be further regiospecifically cyclized. All of these reactions take place with very high stereoselectivity.

The addition of carboxylic acids to terminal alkynes is efficiently catalyzed by the early transition-metal complex Re(CO)(sub 5)Br in toluene or n-heptane at 110 degree C in an air atmosphere, affording the anti-Markovnikov adducts in good yields with high selectivity. The conclusion states that when n-heptane is used as solvent, Re(CO)(sub 5) can be recovered from the reaction mixture.

Research has been conducted on enzyme- and metal-catalyzed reactions. The study of these reactions caried out in investigating asymmetric transformations of acyloxyphenyl ketones to optically active hydroxyphenyl alcohols.

An efficient fluoro biphasic system-based catalysis procedure for atom transfer radical additions has been described. The system utilizes a low valent metal such as copper(I) to induce the radical cleavage of a carbon-halogen bond. Since the cleavage of the carbon-halogen bond is reversible procedure, a new halogenated product can be produced by reductive elimination and the catalyst can then be recovered at the conclusion of the reaction.

The transformation of aldehydes to acylated cyanohydrins is possible by using the stoichiometric amount of the reagent acetyl cyanide or methyl cyanoformate in the presence of the catalyst Bu3SnCN. During the reaction process Bu3SnCN binds to the aldehyde and Bu3Sn(O-i-Pr) reacts with acetyl cyanide to regain Bu3SnCN.

Chemoselective reduction of nitroarenes and tertiary aliphatic nitro compounds by viologen-controled sodium dithionite reduction results in the formation of anilines and hydroxylamines. The moderate reaction conditions have no effect on carbonyl and ester groups. In the absence of viologen no reduction takes place. Experimental data reveals that reduction of an aromatic nitro group to an amino group is rapid in acetonitrile-water compared to that in dichloromethane-water.

The cyclization of phenylthioacetals over ZnCl2-promoted montmorillonite clay generate the benzo(b)thiophene in moderate amount and its derivatives. Diphenyl disulfide and other undefined products are obtained. The coordination of phenylthioacetals with active sites of the catalyst through the oxygen atom and bimolecular processes lead to the generation of diphenyl disulfide. Application of the vapor phase technique at 200 to 300 degrees centigrade provides an improved synthesis of benzothiophene and its derivatives through intramolecular cyclizations.

Organolithium reagents enable the synthesis of amines from substituted aminomethyl sulfides with high yields. N-substituted aminomethyl sulfides are synthesized into secondary amines through imines as intermediates while N,N-disubstituted aminomethyl sulfides are synthesized into tertiary amines through aminocarbenes.

A heterogeneous catalyst can be used to obtain carboxylic acids in a regioselective fashion, in the presence of formic acid or oxalic acid and phosphine ligands. A catalytically-active palladium phosphine species may develop due to the possible leaching of the metal from the solid by the phosphine ligand. A portion of the reaction can take place on the surface of the solid. The surface of the solid phase may retain a colloidal phosphine-palladium species, developed by the phosphine ligand.

The synthesis of 23,24-dioxa-5-oxophlorin involves the condensation of 2,2'-difurylmethane with diformyl dipyrryl ketone, followed by extraction and chromatography in neutral alumina. The low yield from trifluoroacetic acid- chloroform catalyst system can be raised to 17% by using hydrobromic acid and acetic acid. Oxophlorins are keto tautomers of meso-hydroxyporphyrins and are intermediates in the synthesis of porphyrins. The dioxa derivatives, however, do not react with acetic anhydride-pyridine as the mother oxophlorin does to give acetoxyporphyrin analogues.

Nickel(0) catalyzes the cross coupling of aryl O-carbamates and triflates with Grignard reagents to give polysubstituted aromatics. The substrates are easily obtained from phenols and halides and are interconvertible. The carbamates, singly or conjugated, are effective in directed ortho metalation (1,2-dipole-like) while the triflates are more effective with sterically restricted cases. The use of triflates also minimizes the usual beta-hydrogen elimination. This Ni-mediated coupling, in effect, provides a facile and regiospecific route to complex polysubstituted aromatics.

A hydrated Sharpless reagent (1:2 Ti/chiral tartrate) allows the resolution of (+/-)-5-(3, 5-di-t-butyl-4-hydroxyphenyl)methyl-4-thiazolidinone, prepared from 3, 5-di-t-butyl-4-hydroxybenzaldehyde and rhodanine. When (+)-tartrates are used, the tert-butyl hydroperoxide oxidizes the (+)-enantiomer faster, leaving a (-)-enriched ketone. Conversely, using (-)-tartrates leaves behind a (+)-enriched ketone. The 94% enantiomeric purity is further enhanced by crystallization, which precipitates only the enreacted racemic ketone. The bulkier diisopropyl tartrate gives a 5% better optical yield than diethyl tartrate.

The cyclic dithioacetal oxides of aryl aldehydes undergo nickel-catalyzed croos-coupling with Grignard reagents to form olefins via two different routes. In the presence of an acidic proton at C-2, a Pummerer-type rearrangement initially occurs, followed by concurrent alkylation and double bond formation. Where the C-2 carbon is already functionalized with an alkyl or aryl group, Pummerer-type rearrangement is either unneeded or impossible and the oxide undergoes direct alkylative olefination to yield the same type of products.

The enantioselective resolution of beta-amino alcohols with the Katsuki- Sharpless catalyst is due to complexation, not to oxidation. A stereochemical experiment reacts N, N-dimethyl-2-aminoethanol (HDMAE) and five analogous alcohols with titanium diisopropyltartrate isopropionate Ti2DIPT(OiPr)4, yielding the pentacoordinated TiDMAE(OiPr)3. On addition of H2DIPT, a more stable complex Ti2(DIPT)2DMAE(OiPr)3 results. The spectroscopic signals clearly show highly enantioselective coordination of the chiral alkoxide and amino groups to the two metal atoms. Such specificity enables the assignment of absolute confgurations to the beta-amino alcohols.

The synthesis of trisubstituted olefins using rhodium fluoropatite catalyst is described. The wide scope of this reaction is demonstrated by converting a variety of arylboronic acids and Baylis-Hillman adducts to trisubstituted olefins.

The oxidative coupling of triarylmethanols with internal alkynes using rhodium catalyst is described. The reaction results in cleavage of C-H and C-C bonds to produce naphthalene derivatives.

Asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides and N-arylmaleimides using axially chiral BINIM- Ni complexes as catalyst are described. The reaction seems to give a good yield of corresponding adducts with high enantioselectivities.