Highly stereoselective palladium-catalyzed Heck coupling of 5-iodouridine-5′-triphosphates with allylamine: a new efficient method for the synthesis of (E)-5-aminoallyl-uridine-5′-triphosphates

The palladium-catalyzed Heck coupling of 5-iodouridine-5′-triphosphates with allylamine is described. The reaction is highly stereoselective that results in high purity of (E)-5-aminoallyl-uridine-5′-triphosphate with good yields.     

Environmentally friendly and efficient method for the synthesis of the new α,α′-diimine ligands with benzimidazole moiety

The new α,α′-diimine ligands with benzimidazole moiety were synthesized based on the rearrangement of 3-aroylquinoxalin-2(1H)-ones when exposed to 4,5-diamino-2,1,3-benzoxadiazole, 4,5-diamino-2,1,3-benzothiadiazole and 5,6-diaminoquinoxaline. Among them, we report the first examples of the new heterocyclic system namely benzo[4′,5′]imidazo[1′,2′:1,2]quinolino[3,4-b and 4,3-b][1,2,5]oxadiazolo[3,4-f]quinoxalines, which exhibits an interesting electrochemical behavior. All compounds were fully characterized by IR, ¹H and ¹³C NMR spectroscopies, and mass spectrometry.     

Efficient method for the synthesis of dideoxyuridine-5′-triphosphate fluorescent derivative

An approach to the synthesis of a fluorescent labeled dideoxyuridine triphosphate derivative using the pentafluorophenyl ester of a dicarbocyanine dye was suggested. The use of the dye pentafluorophenyl ester instead of N-oxysuccinimidyl one has the advantage of giving significantly higher yield of the fluorescent labeled dideoxyuridine-5??-triphosphate derivative.     

A new method for the synthesis of β-halonitroalkanes

Summary A new method is elaborated for the synthesis of -chloronitroalkanes; it consists in the reaction of phosphorus pentachloride with acetals obtained by the addition of primary -nitro alcohols to vinyl alkyl ethers.     

Highly efficient synthesis of α-amino amidines from ynamides by the Cu-catalyzed three-component coupling reactions

Using ynamides as one of the reacting components, the Cu-catalyzed three-component reaction of sulfonyl or phosphoryl azides and amines affords α-amino amidines in high yields under mild conditions. Synthetic utility of the produced compounds was demonstrated in the diastereoselective alkylation of α-amino amidines bearing a chiral oxazolidinone moiety. It was also shown that α-amino imidates could be readily prepared by employing alcohols instead of amines.     

Reactions of acyl phosphonates with organoaluminum reagents: a new method for the synthesis of secondary and tertiary α-hydroxy phosphonates

The reactions of organoaluminum reagents (trimethylaluminum, triethylaluminum, etc.) with aryl and alkyl acyl phosphonates, which lead to the formation of α-hydroxy phosphonates in moderate to good yields, are reported. This method provides easy access to secondary and tertiary α-hydroxy phosphonates depending on the reaction conditions. The reactions of triethylaluminum with a series of acyl phosphonates at 0 °C gave the secondary α-hydroxy phosphonates, while at −100 °C they afford the tertiary α-hydroxy phosphonates.     

First example of the coupling of α-diazoketones with thiourea: a novel route for the synthesis of 2-aminothiazoles

α-Diazoketones undergo smooth coupling with thiourea in the presence of 10 mol % of copper(II) triflate to produce the corresponding 2-aminothiazoles in excellent yields with high selectivity. The use of copper(II) triflate makes this method simple, convenient and practical. This method works well with both aryl and alkyl diazoketones to furnish a wide range of 2-aminothiazoles.     

Development of a scalable palladium-catalyzed α-arylation process for the synthesis of a CGRP antagonist

The Pd-catalyzed α-arylation of cycloheptapyridyl ketone is a key complexity-building step in the synthesis of BMS-846372, a CGRP antagonist. A first-generation process utilized Pd(OAc)₂/P^tBu₃·HBF₄ catalyst system with a strong base NaO^tBu. Although this process was demonstrated on multi-kilo scale, the harsh conditions led to non-selective metal catalyzed processes, which generated several operational, quality, and throughput issues. By acquiring detailed knowledge around several important process parameters, we were able to design an efficient and scalable second-generation α-arylation process using a Pd(OAc)₂/RuPhos catalyst system with the weaker base, K₃PO₄ in tert-amyl alcohol. This new weak base process was high yielding, efficient, and superior in several respects compared to the strong base process. The strategy behind the reaction and isolation development and the process considerations important to scaling a catalytic reaction from laboratory to manufacturing scale will be discussed.     

A highly efficient method for the resolution of 8,8′-dihydroxy-1,1′-binaphthyl

The diastereomeric mixture of monoesters of racemic 8,8′-dihydroxy-1,1′-binaphthyl and N-CBZ-l-proline was easily separated. Each diastereomer gave enantiomerically pure (R)- or (S)-8,8′-dihydroxy-1,1′-binaphthyl in good yields after hydrolysis.     

One-pot synthesis of a rose-like Pd–Fe3O4 nanocatalyst for Sonogashira coupling reactions

A one-pot synthesis of rose-like Pd–Fe₃O₄ nanocomposites via the controlled thermal decomposition of Fe(CO)₅ and reduction of Pd(OAc)₂ is reported. This rose-like Pd–Fe₃O₄ composite structure has a high surface area owing to the individual Pd–Fe₃O₄ nanosheets, which imparted a high catalytic activity for Sonogashira coupling reactions. Moreover, the catalyst also demonstrated magnetic recyclability.     

Highly diastereoselective Friedel-Crafts reaction of arenes with N-tert-butanesulfinylimino ester towards the efficient synthesis of α-arylglycines

Lewis acid-catalyzed highly diastereoselective asymmetric Friedel-Crafts alkylation of arenes with a chiral N-tert-butanesulfinylimino ester is described. The reaction can be accomplished with ease in the presence of a catalytic amount of In(OTf)(3) at room temperature, providing a series of enantiomerically enriched α-arylglycines in good yields and with excellent diastereoselectivities (up to 99% de). Highly stereoselective double Friedel-Crafts alkylation to afford dialkylation product was also investigated.     

New method for the synthesis of 2-substitutedN, N′-diacylimidazolidines

A method for the synthesis of 2-substitutedN, N′-diacylimidazolidines was developed. The method is based on the reactions of acylating reagents (carboxylic acid chlorides and anhydrides, sulfonic acid chlorides, a carbamic acid chloride, and ethyl chlorocarbonate) with Schiff's bases prepared by the reaction ofN-acylethylenediamines with aldehydes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya. No. 5, pp. 896–900, May, 2000.     

A new method for the synthesis of organic–polyoxometallate hybrid compounds

The reaction of the Na₂MoO₄ or Na₂WO₄ salt with organic amine and PCl₅, SiCl₄ or TiCl₄ in hydrochloric acid medium under hydrothermal conditions yields organic–polyoxometallate hybrid compounds, with the following reaction formula: Na₂MO₄ + Lewis-base + XCl_n + HCl → (Lewis-baseH)_m(XM₁₂O₄₀) + NaCl + H₂O (M = Mo or W; X = P, Si, Ti,; n = 3–5). By using this method, four new complexes, [(CH₃)₂NH]₃[H₃PW₁₂O₄₀] (1), (C₂H₅OH)₃(H₃PMo₁₂O₄₀) (2), [DMDA]₂[H₄SiW₁₂O₄₀]·H₂O (3) (DMDA = 1 N,3 N-dimethyl-1,3-diazolidine) and [(DAN)₆][H₄TiW₁₂O₄₀]·4H₂O (DAN = 4,4′-dianiline) (4), were obtained, and their crystal structures are reported. Thermal analysis of 1, 2 and 4 has been carried out. The thermal analysis indicates that the Keggin anion skeleton begins to decompose at about 300 °C. The possibility of constructing hydrogen-bond interactions by association between the polyoxometallate and the organic compound is explored. The roles of solvents and organic groups in the formation of specific crystalline architectures are discussed. The crystal structure of [H₄TiW₁₂O₄₀], a hetero-transition-metal Keggin polyoxometallate with a square-plane TiO₄, has been reported. Four architectures developed by hydrogen-bond associations of different Keggin polyoxometallates and organic bearing N–H or O–H donor functions are described. The selected organic modules (4,4′-dianiline, 1,3-dimethylimidazolidine, dimethylamine and ethanol) possess hydrogen-donor functions to allow them to act as bridges between polyoxometallate groups. Depending on the nature of the donor group, the number of hydrogens available for bonding, the geometric features and the sizes of the organic modules, diverse assembling patterns have been observed ranging from one-dimensional to three-dimensional networks. For all the networks, H₃O⁺ and H⁺ act as actual linkers between the molecular units.     

An efficient method for the synthesis of enantiopure cis-α,β-epoxy acids

Enantiopure cis-α,β-epoxy acids were prepared via a modified Darzen's reaction employing the titanium-mediated bromination–aldolization of chiral acetate thioimide enolate.     

Studies on the asymmetric synthesis of huperzine A. Part 2: Highly enantioselective palladium-catalyzed bicycloannulation of the β-keto-ester using new chiral ferrocenylphosphine ligands

New chiral ferrocenylphosphine ligands were designed and tested in the enantioselective bicycloannulation of β-keto-ester 2 with bifunctional allylic agent 4. A range of e.e. values from 80 to 90% of the bicyclic intermediate 6 was achieved. Subsequently, enantiopure (−)-huperzine A was prepared in ca. 40% yield from β-keto-ester 2.     

Total synthesis and assignment of the absolute stereochemistry of xanthoangelol J: development of a highly efficient method for Claisen–Schmidt condensation

The first total synthesis of cancer chemopreventive terpenyl hydroxychalcone xanthoangelol J isolated from Angelica keiskei was accomplished with asymmetric epoxidation, aromatic C-alkylation and Claisen–Schmidt condensation via enol mode as key steps. The crucial Claisen–Schmidt condensation has been accomplished by a novel green method using KHSO₄–SiO₂ as a recyclable catalyst under microwave activation. The absolute configuration of the molecule was also determined.     

A new efficient route for the synthesis of 4,4′,6,6′-tetra(azido) azo- 1,3,5-triazine

A new method for the synthesis of 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine(TAAT)is described.The key intermediate 4,4′,6,6′- tetra(azido)hydrazo-1,3,5-triazine(TAHT)was synthesized by nucleophilic substitution in the case of sodium azide as nacleophile. N-Bromosuccinide(NBS)was used as oxidant to oxidize TAHT by a tractable operation under mild reaction condition.The target compound TAAT was obtained with a facile process and high overall yield of 81%.The structures of TAAT and its intermediates were identified by spectroscopic methods.     

New method for the synthesis of α-chlorocinnamonitriles

A novel method for the preparation of nitriles of -chlorocinnamic acid from aldehydes and ketones was proposed. Transformation of carbonyl compounds into hydrazones followed by treatment of the reaction mixture with CCl₃CN in the presence of copper chloride(i) yields -chlorocinnamonitriles.     

Simple and effective method for the synthesis of 3′,5′-substituted 1-β-D-arabinofuranosyluracil

3,5-Substituted arabinofuranosyluracil is a starting compound in 2-modifications. A convenient and effective method is proposed for the synthesis of 1-(3,5-di-o-trityl--D-arabinofuranosyl)uracil by successive reactions of 2,2-cyclization of uridine, 3,5-tritylation of the 2,2-anhydrouridine, and hydrolytic cleavage of the 2,2-anhydro bond.Institute of Organic Synthesis, Riga LV-1006. Odense Universitet, Kemisk Institut, Odense, Denmark. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 975–977, July, 1996. Original article submitted April 25, 1996.     

Asymmetric synthesis of enantiopure isoxazolidinone monomers for the synthesis of β-oligopeptides by chemoselective amide ligation

The design and general synthesis of enantiopure isoxazolidinone monomers as precursors for the preparation of enantiopure N-terminal hydroxylamine-β³-oligopeptides, which may be used as reaction partners with α-ketoacids in the decarboxylative amide ligation reaction, is described.