Facile and selective deallylation of allyl ethers using diphosphinidenecyclobutene-coordinated palladium catalysts

(pi-Allyl)palladium triflate bearing a 1,2-bis(4-methoxyphenyl)-3,4-bis(2,4,6-tri-tert-butylphenylphosphinidene)cyclobutene ligand (DPCB-OMe), [Pd(eta(3)-C(3)H(5))(DPCB-OMe)]OTf, efficiently catalyzes deallylation of a variety of allyl ethers in aniline to give corresponding alcohols in high yields under mild conditions. The reactions can be performed in air without loss of a variety of functionalities including vinyl, alkynyl, hydroxy, acetoxy, silyloxy, and acetal groups. Allyl 2-allyloxybenzoate selectively undergoes deallylation of the allyloxy group to give allyl salicylate in quantitative yield.     

Facile synthetic protocols for perfluoroalkyl-substituted diazapentaphenes

Novel syntheses of 13,14-bis(perfluoroalkyl)-substituted 5,8-diazapentaphene derivatives were realized by such a facile two-step protocol as consecutive benzyne insertion into C(O)–NH bonds of p-phenylene-bis(perfluoroalkanamides), followed by Friedel–Crafts type cyclization reaction, yielding the corresponding title compounds especially for the case of Rf=CF₃ or C₂F₅. Additionally, an alternative approach based on condensation of cyclohexane-1,4-dione with (o-aminophenyl) perfluoroalkyl ketones, followed by dehydrogenation enabled us to effectively access to the same final products in better yields.     

Facile synthesis of phosphorylated azides in ionic liquids and their use in the preparation of 1,2,3‐triazoles

The facile general synthetic route to azidoalkylphosphonates by the nucleophilic substitution reaction in a series of bromoalkylphosphonates was elaborated, using 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF₆]) as a recyclable reaction medium. These azidoalkylphosphonates were used as intermediates for copper(I)‐catalyzed regioselective 1,3‐dipolar cycloaddition with a variety of alkynes to afford 4‐substituted (1H‐1,2,3‐triazol‐1‐yl)alkylphosphonates as potential drug candidates. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:293–300, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20420     

Synthesis of tetrazoles,triazoles, and imidazolines catalyzed by magnetic silica spheres grafted acid

The magnetically separable catalysts are used in the synthesis of N-containing heterocycles, including tetrazoles, triazoles, and imidazolines. The magnetic silica sphere grafted sulfonic acid (MSS-SO₃H) is suitable for the synthesis of 1,2,3-triazole via the cycloaddition of nitroalkene with NaN₃, whereas the zinc-modified silica sphere catalyst (MSS-SO₃Zn) is more suitable for the synthesis of tetrazoles. The MSS-SO₃Zn catalyst also works well for the synthesis of 2-substituted imidazoline via the condensation of nitriles with ethylenediamine. Both of the MSS-SO₃H and MSS-SO₃Zn catalysts can be recovered easily by a magnet, and they can be reused without further tedious activation.     

Application of the Schmidt reaction for the preparation of tetrazoles (review)

The application of the Schmidt reaction with ketones and nitriles for the preparation of tetrazoles is examined. Modern concepts regarding the mechanism of the reaction of ketones and nitriles with hydrazoic acids are discussed. The range of application of the reaction is indicated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 723–735, June, 1975.     

A mild and general one-pot preparation of cyanoethyl-protected tetrazoles

Described herein is a mild and general one-pot procedure for the conversion of cyanoethyl amides to cyanoethyl-protected tetrazoles with azidotrimethylsilane via the intermediacy of imidoyl chlorides generated in situ with phosphorus pentachloride. This synthetic sequence works well with sterically hindered amides and is compatible with acid sensitive functionality.     

Facile preparation of the oxetane-nucleosides

Efficient and practical large scale synthesis of suitably protected 1',2'-oxetane locked purine and pyrimidine nucleosides for incorporation in oligo-DNA or -RNA by solid-phase synthesis is reported. A high regio and stereoselectivity with preferential formation of the beta-anomer in the glycosylation reaction, using the Vorbrüggen procedure, was achieved by a convergent synthetic procedure with orthogonal protection strategy using either 1,2-di-O-acetyl-3,4-O-isopropylidene-6-O-(4-toluoyl)-d-psicofuranose or 2-O-acetyl-6-O-benzyl-1,3,4-tri-O-(4-toluoyl)-d-psicofuranose as the glycosyl donor.     

Catalytic deallylation of allyl- and diallylmalonates

Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates.     

New synthetic protocols for the preparation of unsymmetrical bisindoles

Novel unsymmetrical bisindoles were synthesized by a solvent-free C-C bond-formation reaction under mild conditions. Starting from aziridines or hydroxyl precursors, indoles have been used as C-nucleophiles to form new pharmacologically interesting bisindoles via an electrophilic aromatic substitution pathway in good to excellent yields. [reaction: see text]     

Facile preparation of Hexahydropyrrolo

Chlorolactames 2a-f reacted with sodium azide to give the cyclopropylketimines 3a-f (75-89%), and acid hydrolysis of 3c,d yielded the cyclopropylketones 6c,d (61-67%). Compounds 3a-f and 6c, d were transformed by heating (170-240 degrees C, sublimation) to the air-sensitive dihydropyrroles 4a-f (51-71%) and dihydrofurans 7c, d (85-91%). Oxidation of the dihydro derivatives 4a-f and 7c,d with DDQ led to novel types of pyrrolo[3,2-e][1,4]diazepinedione derivatives 5a-f (75-84%) and furo[1H][3,2-e][1,4]diazepinediones 8c, d (91-93%).     

1-Isocyanomethylbenzotriazole and 2,2,4,4-tetramethylbutylisocyanide—cleavable isocyanides useful for the preparation of α-aminomethyl tetrazoles

1-Isocyanomethylbenzotriazole and 2,2,4,4-tetramethylbutylisocyanide smoothly undergo Ugi type reaction toward 1,5-disubstituted aminomethyl tetrazoles and can be subsequently cleaved under acidic conditions yielding substituted α-aminomethyl tetrazoles.     

Rhodium-catalyzed imination of sulfoxides and sulfides: efficient preparation of N-unsubstituted sulfoximines and sulfilimines

The Rh(II)-catalyzed imination of sulfoxides and sulfides using [Rh(2)(OAc)(4)] as a catalyst and trifluoroacetamide or sulfonylamides in combination with iodobenzene diacetate and magnesium oxide affords sulfoximines and sulfilimines, respectively, in a stereospecific manner. [reaction: see text]     

Facile method for the preparation of lyso-GM1 and lyso-GM2

This paper reports a facile method for the preparation of lyso-GM1 [Gal beta1-->3GalNAc beta1--> 4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-sphingosine] and lyso-GM2 [GalNAc beta1-->4(Neu5Ac alpha2-->3)Gal beta1-->4Glc beta1-->sphingosine], respectively, from GM1 [Galbeta1-->3GalNAc beta1-->4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-Cer] and GM2[GalNAc beta1-->4(Neu5Ac alpha2-->3)Galbeta1-->4Glc beta1-->1'-Cer], using sphingolipid ceramide deacylase and high performance anion-exchange chromatography (HPAEC). The enzymatically released lyso-GM1 and/or lyso-GM2 was effectively separated from its parent ganglioside by HPAEC using a Mono Q HR 5/5 column with an Amersham Biosciences fast protein liquid chromatography system. The yield was almost quantitative and the separation completed in approximately 3 h. This method is more convenient and effective than the conventional method using alkaline hydrolysis and silicic acid chromatography to generate and purify lyso-gangliosides.     

Fast microwave-assisted preparation of aryl and vinyl nitriles and the corresponding tetrazoles from organo-halides

Aryl and vinyl nitriles have been prepared in very high yields from the corresponding bromides using palladium-catalyzed reactions with microwave irradiation employed as the energy source. Furthermore, flash heating was used successfully for the conversion of these nitriles into aryl and vinyl tetrazoles by cycloaddition reactions. One-pot transformation of aryl halides directly to the aryl tetrazoles could be accomplished both in solution and on solid support. All reactions were completed in minutes rather than in hours or days as previously reported with the standard thermal heating technique. A very potent HIV-1 protease inhibitor (K(i) = 0. 56 nM), comprising two tetrazole heterocycles as carboxyl group bioisosteres, was prepared in one pot by microwave-promoted cyanation of a bromo precursor and a subsequent cycloaddition reaction. The temperature-time profiles at 13, 20, and 60 W magnetron input power in DMF are presented.     

Facile preparation of 3-acetoxycyclobutanone

3-Acetoxycyclobutanone is a versatile intermediate to access cyclobutanes with a variety of substitution patterns. Established procedures require a two step process that includes multiple distillations. We report a one-pot procedure that renders this compound readily available. Additionally, it was determined that copper plays a key role in the reaction sequence.     

Facile preparation of fullerenyl boronic esters

The fullerendiol C₆₀(OH)₂(OOt-Bu)₄ 1 reacts with various arylboronic acids ArB(OH)₂ to form fullerene-containing boronic esters C₆₀(O₂BAr)(OOt-Bu)₄ in up to 95% yield depending on the structure of aryl group. Bis(pinacolato)diboron (B(OCMe₂)₂)₂ also reacts with 1 to form C₆₀(O₂BB(OCMe₂)₂)(OOt-Bu)₄. The bisboronic ester C₆₀(O)(O₂BAr)₂(OOt-Bu)₂ was also obtained starting from a tetrahydroxyl fullerene derivative C₆₀(O)(OH)₄(OOt-Bu)₂. The fullerenyl boronic esters are moderately stable in air. Single crystal X-ray structure of C₆₀(O₂BPh)(OOt-Bu)₄ was obtained.     

Facile preparation of potassium 32P-phosphonate

Simple and easy to operate experimental assemblies were for the first time designed for the successful preparation of potassium ³²P-phosphonate from ³²P-orthophosphate. Phosphate was first converted to phosphoryl chloride by reacting with phosphorus pentachloride. Then the phosphoryl chloride formed was reduced to phosphorus trichloride by heating with charcoal at 650 °C. The latter was absorbed in aqueous potassium hydroxide to obtain potassium ³²P-phosphonate at a yield of about 75%. The chemical purity of ³²P-phosphonate was assayed using ion-chromatography and the radiochemical purity was also determined.The authors thank Shri. J. K. Ghosh, Chief Executive, BRIT and Dr. N. Sivaprasad, General Manager, RPh & ILCJ, BRIT for their support and encouragement throughout this work.     

Facile preparation of fused ring azolylureas

Two novel reagents for the preparation of fused ring azolylureas are presented.     

Facile preparation and properties of superhydrophobic nanocellulose membrane

Superhydrophobic nanocellulose membrane was prepared by synergistically modifying biodegradable nanocellulose with low-carbon perfluoroorganosiloxane and ethyl orthosilicate. The effects of four kinds of low-carbon perfluoroorganosiloxanes with different structures and their ratio to ethyl orthosilicate on the hydrophobic properties of nanocellulose membrane were investigated, and then FT-IR, XPS, XRD, SEM, TEM, AFM, TG and contact angle goniometer were used to characterize the structure and hydrophobic properties of nanocellulose membrane before and after modification. It is found that when the molar ratio of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTMS) to ethyl orthosilicate (TEOS) is 1, the modified nanocellulose membrane PFOTMS-TEOS-CNF is loaded with silica nanoparticles both inside and on its surface, and a micro-nano hierarchical rough morphology with low surface energy is constructed. At this point, the root-mean-square roughness (Rq) of nanocellulose membrane is 112 nm, and the static contact angle of water droplet is 153.5°, successfully realizing superhydrophobicity. In addition, compared to unmodified nanocellulose membrane, PFOTMS-TEOS-CNF with better thermal stability includes an additional maximum weight loss rate temperature (491.2 °C). The above advantages markedly improve the shortcomings of pristine nanocellulose, such as superhydrophilicity and insufficient thermal stability, and also broadens its high-value application in many fields.