Selective N-1 alkylation of unsymmetrically substituted pyrazoles

A series of C-substituted pyrazoles have been N-alkylated. The alkylation occurs preferentially at the N-1 position when a tert-butyl group is present at the pyrazole C-3 position.     

Synthesis of unsymmetrically substituted subphthalocyanines

A series of new unsymmetrically substituted subphthalocyanines containing iodo or octylthioether substituents on the outer aromatic rings have been synthesized. The statistical reaction of one equivalent of 1,2-dicyano-3-iodobenzene whether with two equivalents of 1,2-dicyano-4-octylthiobenzene or with two equivalents of 1,2dicyano-4,5-dioctylthiobenzene in the presence of boron trichloride in 1-chloronaphthalene yielded in both cases all the possible expected unsymmetrically substituted subphthalocyanines, which were separated by column chromatography on silica gel. All compounds were identified by FAB mass spectrometry and then characterized by HR-LSIMS spectrometry. The unambiguous characterization of each constitutional isomer was made possible by careful examination of the symmetry environment experienced by each proton on their 1H-NMR spectra.     

非对称取代脲的合成与应用

总结了合成非对称取代脲的几种方法，分析了各种方法的利弊，介绍了非对称 取代脲的主要应用，指出直接利用一氧化碳进行硒催化的胺与硝基化合物的氧化还 原羰基化反应来合成非对称取代脲的方法是比较有发展前景的方法，并对硒催化的 氧化还原羰基化反应作了较为详细的介绍。     

Synthesis and heteroelectrocyclization of unsymmetrically substituted diazomalonamides

A selective procedure was developed for the synthesis of 1,2,3-triazoles and unsymmetrically substituted diazomalonamides. Cyclization of unsymmetrically substituted diazomalonamides to 1,2,3-triazoles was studied by the method of intramolecular competitive reactions. The kinetic and thermodynamic characteristics of the process were determined. Quantum-chemical calculations for the monorotatory electrocyclic and nonrotatory heteroelectrocyclic mechanisms of cyclization were carried out. N-Aryldiazomalonamides undergo cyclization according to the heteroelectrocyclic mechanism, whereas cyclization of N-alkyldiazomalonamides proceeds by the monorotatory mechanism. The experimental constant of competition between these processes is (1.3—8.3)·10³ (DMSO-d₆) and (45.2—72.4)·10³ (CD₃OD).     

Synthesis of unsymmetrically substituted 4H-1,2,4-triazoles

A general method was developed for the synthesis of unsymmetrically 3,5-disubstituted 4H-1,2,4-tria-zoles (Ph, H or Ph, CH₃) with allyl or benzyl groups in the 4-ring position. The reaction of the corresponding 3,5-disubstituted 1,3,4-oxadiazoles with allylamine or benzylamine gave the desired compounds. The oxadiazoles were prepared by heating at 100° N,N'-diacylhydrazines with phosphorus pentoxide.     

Synthesis of novel push-pull unsymmetrically substituted alkynyl phthalocyanines

Two families of "push-pull" phthalocyanines 1-3 having an unusually strong dipole moment have been prepared. The syntheses of unsymmetrically substituted phthalocyanines 1a,b and 2 bearing one or two electron-withdrawing 4-nitrophenylethynyl moieties, respectively, and six alkoxy substituents were performed by combination of a zinc or nickel templated cyclotetramerization and cross-coupling palladium mediated methodologies. In a similar way, the "push-pull" compounds 3a,b having a reversal substitution pattern, characterized by the presence of one electron-donor 4-(dimethylamino)phenylethynyl unit and six strong acceptor alkylsulfonyl substituents were prepared. The compounds show very large second-order nonlinear optical responses.     

Synthesis of new unsaturated derivatives of functionally substituted 2-imino-2,5-dihydrofurans

5,5-Substituted 2-imino-4-methyl-2,5-dihydrofuran-3-carbonitriles reacted with aromatic aldehydes to give the corresponding 5,5-substituted 2-imino-4-(2-R-vinyl)-2,5-dihydrofuran-3-carbonitriles. The latter were converted into hydrochlorides which were hydrolyzed to 3-cyano-4-(2-R-vinyl)-2,5-dihydrofuran-2-ones whose condensation with malononitrile afforded dicyanomethylidene derivatives.     

Synthesis and characterization of liquid crystalline unsymmetrically substituted phthalocyanines

The synthesis of unsymmetrically substituted phthalocyanines bearing two p-tolyl-sulfonyl (tosyl)amido and six alkylthio moieties was achieved by cyclotetramerisation of two different phthalonitrile derivatives, namely 1,2-di(alkylthio)-4,5-dicyanobenzene and 4,5-dicyano-N,N′-ditosyl-o-phenylenediamine in the presence of an anhydrous metal salt and strong base. The new compounds were characterized by elemental analyses, UV/Vis, IR, NMR and mass spectra. The mesogenic properties of these new materials were studied by differential scanning calorimetry (DSC) and polarizing optical microscopy. The mesogenic properties of these compounds were compared to that of their symmetric analogous, octaalkythia substituted phthalocyanine derivatives.     

Synthesis of unsymmetrically substituted pyrene derivatives through (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane

A straightforward route to unsymmetrically functionalized pyrene derivatives is described involving the synthesis of key precursor (6-bromo-3,8-dibutylpyren-1-yl)trimethylsilane 1. In a first step bromide 1 was successful in Suzuki-Miyaura, Sonogashira, and Buchwald-Hartwig cross-coupling reactions. Subsequent transformation of the trimethylsilyl group to bromide enabled the introduction of a second variable functional group onto the pyrene skeleton.     

2,5-Disubstituted pyrrolidines: versatile regioselective and diastereoselective synthesis by enamine reduction and subsequent alkylation

A direct and versatile route enabling the regio- and diastereoselective synthesis of 2,5-disubstituted pyrrolidines by reduction of enamines derived from pyroglutamic acid is reported.     

Synthesis of symmetrically and unsymmetrically substituted S,S-dialkyl phosphonodithioates

Herein, we report the synthesis of a range of S,S-dialkyl phosphonodithioates. Symmetrically substituted analogues were readily prepared from the corresponding phosphonic dichlorides in good to moderate yields, while unsymmetrically substituted variants were obtained by a sequential alkylation-deprotection-alkylation strategy.     

Direct synthesis of imines from gem-dibromomethylaryl derivatives: application to unsymmetrically substituted bipyridine frameworks

An efficient methodology for the one-pot synthesis of imines is described starting from gem-dibromomethylaryl compounds and primary amines. The synthesis was applied to various aliphatic mono- and polyamines as well as to electron-rich anilines. The protocol was extended to 6-bromo-5'-dibromomethyl-2,2'-bipyridine to afford the corresponding imines. With n-propyl- and n-decylamine, further conversion, in three steps, to the corresponding 6-carboxy-5'-alkylaminomethyl-2,2'-bipyridine derivatives was selectively achieved, providing new tridentate ligands that may find interesting applications for the complexation of lanthanide(III) cations in their anionic or zwitterionic form.     

Synthesis and optical properties of novel unsymmetrically substituted benzothiadiazole-based luminophores

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Synthesis of unsymmetrically substituted 2,2'-dihydroxy-1,1'-biaryl derivatives using organic-base-catalyzed Ferrier-type rearrangement as the key step

A strong organic base, TBD, functioned as a unique catalyst for the intramolecular multi-step transformation of lactols using the Ferrier-type rearrangement as the key step to provide unsymmetrically substituted 2,2'-dihydroxy biaryl compounds having four ortho substituents about the biaryl axis without the need for a metal catalyst.     

Synthesis of unsymmetrically substituted dodecakis(trifluoroethoxy)-phthalocyaninato vanadyl complexes

Three novel unsymmetrical vanadyl dodecakis(2,2,2-trifluoroethoxy)phthalocyaninates with nitro, amino or with no substitution were synthesized by a statistical condensation of 3,4,5,6-tetrakis(2,2,2-trifluoroethoxy)phthalonitrile with 4-nitro, 4-amino or 4-unsubstituted phthalonitrile, and separated by common column chromatography. These highly soluble phthalocyanines were characterized by elemental analysis, ir and ¹H-nmr, uv-visible and fast-atom-bombardment mass spectroscopy. Their uv-visible absorption spectra in solution and in doped poly(methyl methacrylate) films showed that they were less aggregated unsymmetrical phthalocyanines.     

Aza-bridged bis-1,10-phenanthroline acyclic derivatives: synthesis, structure, and regioselective alkylation

A family of acyclic aza-bridged bis-1,10-phenanthroline compounds has been synthesized in a convenient way. The resulting compounds 2 and 2·HCl were fully characterized and their solid state structures and NMR spectroscopic properties were investigated to assess how the structural units affect the alkylation reactions. The results reveal the transoid structure for 2. The broadening NMR peak in 2 is shown to be due to an unusual intramolecular CH?N hydrogen bond. This unique conformation offers an efficient and regioselective method to prepare the amino-substituted bis-2,2′-1,10-phenanthroline derivatives and 1,10-phenanthrolino-N-alkylated compounds.     

Novel synthesis of unsymmetrically substituted s-tetrazines

The synthesis of unsymmetrical 3-aryl and 3-heterocyclic s-tetrazines has been examined and the scope of the reaction and the product distribution is discussed. The products included unsymmetrical and symmetrical s-tetrazines, hydrazines, diimides, tetrazoles and triazoles with the composition of the mixtures with respect to structural type varying with the individual reactions. Some transformations with the system are discussed.