Studies on the total synthesis of sanglifehrin A: stereoselective synthesis of the C(29)-C(39) fragment

A highly stereoselective synthesis of the C(29)-C(39) fragment of the potent immunosuppressant sanglifehrin A has been accomplished by a sequence involving 16 steps (18% overall yield) from N-propionyloxazolidinone 9. Key steps are a diastereoselective hydroboration, and a diastereoselective epoxidation of an allylic alcohol followed by a 1,5-anti boron-mediated aldol reaction of methyl ketone 4 with chiral aldehyde 5.     

Highly efficient one-pot,three-component synthesis of 1, 5-benzodiazepine derivatives

A general, mild and efficient protocol for the synthesis of ethyl 4-methyl-2-（thiophen）-2,5-dihydro-1,5- benzodiazepine-3-carboxylate is achieved for first time using H3PMo12O40 in ethanol at 0 ℃ by a one- pot, three-component condensation of various thiophene aldehydes, substituted o-phenylenediamines and ethyl acetoacetate. Compared with the conventional synthesis method, this procedure has the advantages of convenient operation, excellent yields, and environmentally benign. A plausible formation mechanism has been proposed. The structure of the products is characterized by1H NMR, IR, MS and elemental analysis.     

A two-step synthesis of 1,5-disubstituted tetrazoles containing a siloxy or sulfonamide group

A simple two-step route to the synthesis of 1,5-disubstituted tetrazoles containing a β-siloxy or β-sulfonamide group is presented. The synthesis takes place via an isocyanide-based multicomponent reaction and allows incorporation of a wide variety of substitution patterns starting from commercially available reagents. This is followed by cyclization of the ketenimines with trimethylsilyl azide without using any catalyst or activation.     

An Improved Synthesis of Oxazinones Using Molecular Sieves

Abstract: Oxazinones are important chiral reagents in the synthesis of both proteinogenic and nonproteinogenic amino acids. Large scale synthesis of oxazinones has been a problem. The use of molecular sieves in the final step to remove ethanol has helped to obtain the cyclized product in three hours.     

Facile Alternative Synthesis of 1-Alkyl-5-alkylamino-6-phenethyluracils

A short alternative synthesis of 1-alkyl-5-alkylamino-6-phenethyluracil is described in 47% overall yield of 1a via five steps starting from commercially available 6-methyluracil.     

α -(4 -Nitro Phenoxy) Chalcones As Synthons for Cis-(±)-1,5-Benzothiazepines

α-(4 -Nitro Phenoxy) chalcones, V have been utilized as intermediate for the synthesis of some new cis- (±) -2-aryl-3-(4-nitro phenoxy)-4-phenyl-l,5-benzothiazepine VI by cycloconden-sation of 2-amino thiophenol in the presence of mild base.     

Environment-friendly synthesis of N-phenylpiperidine from aniline and 1,5-pentanediol over γ-Al2O3 catalyst

An efficient environment-friendly synthesis of N-phenylpiperidine was developed from aniline and 1,5-pentanediol over γ-Al2O3 catalyst under atmospheric pressure. The conversion of 1,5-pentanediol reached 97% and the selectivity for N-phenylpiperidine attained 94%. The structure of the catalyst was characterized by NH3-TPD and BET. The influences of calcination temperature of the catalyst and reaction temperature on activity and selectivity of the catalyst were investigated.     

Sulfanilic acid catalyzed solvent-free synthesis of 1,5-benzodiazepine derivatives

Sulfanilic acid has been found to be an efficient catalyst for the synthesis of 1,5-benzodiazepines from o-phenylenediamine and ketones. This method is simple, effective and environmentally friendly and gives better yields.     

Reactions with pyrrolidine-2,4-diones,I. New synthesis of pyrano[2,3-c]pyrrole and pyrrolo[3,4-b]pyridine systems

The synthesis of some substituted 4-hydroxy-2,5,6,7-tetrahydro-pyrano[2,3-c]pyrrole-2,5-diones (5) and 4-hydroxy-1,2,6,7-tetrahydro-5H-pyrrolo[3,4-b]pyridine-2,5-diones (6) by reacting 1,5-diaryl-pyrrolidine-2,4-diones (1) and 1,5-diaryl-1,5-dihydro-4-amino-2H-pyrrol-2-ones (3) with bis-2,4,6-trichlorophenyl malonates (4) is described.Dedicated to Prof. Dr. Dr. h. c.O. Kratky, Graz, on the occasion of his 80th birthday.     

Electrochemical study of 1,5-diphenylcarbazide and 1,5-diphenylcarbazone in 0.3 M HClO4

Diphenylcarbazide (DPCI) or diphenylcarbazone (DPCO) is introduced into carbon paste electrodes in order to determine the potential ranges where the oxidation-reduction processes of these species occur in 0.3 M HClO₄. The potential controlled electrolysis was performed for DPCI and DPCO dissolved in 0.3 M HClO₄. From the coulometric results and the UV-visible spectral data of the solution before and after the electrolysis it is possible to establish that DPCI is oxidized in an irreversible process giving diphenylcarbadiazone (DPCDO). DPCO is probably an intermediate in this oxidation, but its concentration is never high because it is slightly more easily oxidized than DPCI. DPCO can be reduced to DPCI at about 0.2 V (ECS) and, finally, DPCDO can be reduced to DPCI at about −0.5 V (ECS). Again, DPCO is probably an intermediate but is not detected because it is so much more easily reduced than DPCDO.     

New [e]-Fused Caffeines: A Simple Synthesis of 3-Substituted [1,2,4]Triazolo[4,3-e]purines

Summary.  A convenient synthesis of 3-substituted [1,2,4]triazolo[4,3-e]caffeines by oxidative cyclization of 8-arylmethylenehydrazinocaffeines with bromine in acetic acid in presence of sodium acetate is described. Corresponding author. E-mail: haney_sami@mail.com Received May 6, 2002; accepted June 13, 2002     

Copper(I)-Catalyzed Tandem Cyclization/Condensation Reaction to Novel 4,5-Dihydropyrazolo[1,5-a]quinolines and Pyrazolo[1,5-a]indoles

A facile copper(I)-catalyzed tandem reaction for the synthesis of 4,5-dihydropyrazolo[1,5-a]quinolines and pyrazolo[1,5-a]indoles is reported here. High efficiency and good yields are displayed in this transformation under mild reaction conditions.      

Synthesis and Reactivities of 1,5- and 1,7-Azulenequinone Derivatives. A Highly Convenient,One-Pot Synthesis of 3-Bromo-1,5- and −1,7-Azulenequinones by Bromination of Azulene,

A very convenient, one-pot synthesis (over 80% yield) of 3-bromo-1,5- and ?1,7-azulenequinones has been developed by bromination of azulene in aqueous tetrahydrofuran. Reduction of 3-bromo-1,5- and ?1,7-azulenequinones with tin or zinc powder in acetic acid gave the parent 1,5- and 1,7-azulenequinones, and further reduction products.     

Microwave promoted a green protocol for solvent free synthesis of 1,5-benzothiazepine and [1,3,4]-thiadiazepine derivatives incorporating thiophene moiety

Abstract

An efficient and environmentally benign procedure is developed for the synthesis of 1,5-benzothiazepine and 1,2,4-triazolo[3,4-b][1,3,4] thiadiazepine derivatives in good to excellent yield under solvent-free microwave irradiations using silica sulfuric acid or basic alumina respectively as solid supports.     

Synthesis of 4-aryl-1,3-diphenyl-1,4,5,10-tetrahydropyrazolo-[3,4-b][1,5]benzodiazepines

A convenient method is proposed for the synthesis of the previously unknown 4-aryl-1,3-diphenyl-1,4,5,10-tetrahydropyrazolo[3,4-b][1,5]benzodiazepines by cyclocondensation of 5-(2-aminoanilino)-1,3-diphenylpyrazole with aromatic aldehydes. The reaction only takes place very selectively with aldehydes which contain electron acceptor substituents in the aryl fragment. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 913–918, June, 2006.     

Iridium‐Catalyzed Enantioselective Allyl–Allylsilane Cross‐Coupling

An enantioselective allyl–allylsilane cross‐coupling involving racemic branched allylic alcohols and allylsilanes is reported. An iridium‐(P,olefin) phosphoramidite complex enables the transformation with high regio‐ and stereoselectivity under operationally simple conditions. The utility of the coupling is demonstrated in a concise catalytic, enantioselective synthesis of a pyrethroid insecticide protrifenbute.     

A scalable synthesis of 1-amino-5-cyanonaphthalene,a precursor for a nitric oxide probe(NO550) designed via the "dye assembly" principle

A convenient and scalable synthesis of l-amino-5-cyanonaphthalene was described.     

Procedure-Controlled Selective Synthesis of 5-Acyl-2-iminothiazolines and their Selenium and Tellurium Derivatives by Convergent Tandem Annulation

Concise and selective: The procedure-controlled synthesis of the title compounds has been achieved for the first time by an organolithium-promoted convergent tandem annulation involving readily available terminal alkynes, chalcogen elements (S, Se, and Te), carbodiimides, and acid chlorides. A novel 1,5-acyl migration is considered to be essential for this useful transformation.     

PTSA catalyzed synthesis of functionalized dipyrazolo[1,5]diazocine-3,8-diones via the reaction of 3-aminopyrazolone with benzaldehyde derivatives

A simple procedure for the synthesis of dipyrazolo[1,5]diazocine-3,8-diones was developed via the one-pot reaction of 3-aminopyrazolone with substituted benzaldehydes in the presence of catalytic p-toluenesulfonic acid (PTSA).     

Water-Mediated Selective Synthesis of Pyrazolo[1,5-a]quinazolin-5(4H)-ones and [1,2,4]Triazolo[1,5-a]quinazolin-5(4H)-one via Copper-Catalyzed Cascade Reactions

A convenient and sustainable synthesis of pyrazolo[1,5-a]quinazolin-5(4H)-ones and [1,2,4]triazolo[1,5-a]quinazolin-5(4H)-one through copper-catalyzed cascade reactions of 2-bromobenzoates with 1H-pyrazol-5-amines or 1H-1,2,4-triazol-5-amine under ligand-free conditions in water is presented. It is notable that aqueous medium turned out to be crucial for the chemoselective formation of the title compounds. Compared with literature protocols, this new method showed advantages such as simple and sustainable procedure, commercially available starting materials, and convenient reuse of the reaction medium together with the copper catalyst.