Synthesis of a New Cyclophane Host and Crystal Structures of Its Compounds with Neutral Guests

A new cyclophane host molecule 3 is prepared by connecting the oxygenatoms of two,-di(4-hydroxyphenyl)-1,4-diisopropylbenzene units withtwo trimethylene spacers. Solid-state structures are determined forcompounds of 3 with dichloromethane and p-xylene guests. The crystals of thetwo host-guest compounds are isomorphous.     

Synthesis and properties of novel aromatic polyamides based on “multi-ring” flexible dicarboxylic acids

The five benzene rings-containing (hereafter referred to as “five-ring”) dicarboxylic acids α,α′-bis[4-(4-carboxyphenoxy)phenyl]-1,4-diisopropylbenzene (p- III ) and α,α′-bis[4-(4-carboxyphenoxy)phenyl]-1,3-diisopropylbenzene (m- III ) were prepared by the fluoro-displacement of α,α′-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene and α,α′-bis(4-hydroxyphenyl)-1,3-diisopropylbenzene with p-fluorobenzonitrile, and subsequent alkaline hydrolysis of the intermediate dinitriles. A number of high-molecular-weight polyamides based on these two “five-ring” dicarboxylic acids (p- III and m- III ) and various aromatic diamines were directly synthesized in N-methyl-2-pyrrolidone (NMP) containing lithium chloride (LiCl) or calcium chloride (CaCl₂) using triphenyl phosphite and pyridine as condensing agents. These polyamides were obtained with inherent viscosities above 0.51 and up to 0.91 dL/g. The weight-average molecular weight were in the range of 51,000–211,000. Most of these polyamides were amorphous and readily soluble in polar solvents such as NMP, N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), and afforded tough, flexible, and transparent films by solution-casting. The films had tensile strength of 50–83 MPa, elongation to break of 4–8%, and tensile modulus of 1.3–2.0 GPa. Most polyamides showed distinct glass transitions on the differential scanning calorimetry (DSC) curves ranging from 147 to 177°C. In nitrogen or air, all the polymers showed no significant weight loss up to 490°C, as indicated by thermogravimetric analysis (TG). © 1996 John Wiley & Sons, Inc.     

Synthesis of New Cyclophane Host Molecules and Crystal Structures of Their Compounds with Hydrocarbon Guests

Three new cyclophane host molecules 2, 4, and 6 are prepared by connecting the oxygen atoms of two ,'–di(4-hydroxyphenyl)-1,4-diisopropylbenzene units with two di-, tetra-, and hexamethylene spacers, respectively. Solid-state structures are determined for host 2 with a hexane guest, host 4 with a toluene guest and a solvating toluene molecule, host 4 with a p-xylene guest,and host 6 with two p-xylene guests.     

新型结构聚芳亚胺的合成与热性能分析

通过傅-克酰化反应得到1,4-双（4′-溴苯酰基）苯,以1,4-双（4′-溴苯酰基）苯和α,α′-双（4′-氨基苯基）-1,4-二异丙基苯为单体,通过钯催化的胺基化反应缩聚合成了含异丙基的聚亚胺酮（pr-PIK）.再以pr-PIK和苯基锂为底物,通过亲核加成反应得到新型结构聚合物——含异丙基的聚醇胺（pr-PAI）.聚合物结构通过FT-IR、1H NMR和元素分析表征,表征结果与目标产物吻合良好.pr-PIK和pr-PAI的热性能由DSC和TG测定,结果表明pr-PIK和pr-PAI具有良好的热稳定性,玻璃化温度大于150℃,热分解温度大于480℃.     

Synthesis of conjugated (1E,3E)- and (1Z,3Z)-1,4-di(n-pyridyl) (or n-quinolyl)-1,3-butadienes from n-(2′-chloroethenyl)pyridine (or quinoline)

The homocoupling reaction between the conjugated n-(2-chloroethenyl)pyridine; n, 2-, 3- and 4- (or quinoline; n, 2- and 4-) mediated by zero-valent nickel complexes at room temperature affords to the corresponding 1,4-diaryl-1,3-butadiene, always as the 1E,3E stereoisomer. The yield in 1,4-diaryl-1,3-butadiene increases with the nickel catalyst and hence, the active zero-valent nickel catalyst is not regenerated during the homocoupling reaction.The stereospecific synthesis of (1Z,3Z)-1,4-di(4′-pyridyl)-1,3-butadiene stereoisomer was efficiently carried out by partial hydrogenation of the appropriate 1,4-di(4′-pyridyl)-1,3-butadiyne.     

Macrocyclic cyclophanes with two and three alpha,omega-dichalcogena-1,4-diethynylaryl units: syntheses and structural properties

By means of four- and six-component cyclization reaction various cyclophanes were synthesized. The components were the di(lithium) salts of 1,4-di(ethynyl)benzene (11), 4,4'-di(ethynyl)biphenyl (13), 1,4-di(ethynyl)-2,5-di(n-hexyl)benzene (18), and 1,4-di(ethynyl)-2,5-di(n-propyl)benzene (19). These building blocks were reacted with alpha,omega-dithiocyanato-n-alkanes and alpha,omega-diselenocyanato-n-alkanes with n = 3-6. In the case of 10 also 1,1'-di(2-thiocyanatoethyl)cyclohexane (24) was reacted to afford a cyclophane comprising three subunits of 11. From most of the resulting macrocyclic cyclophanes (4(n) (n = 3, 5), 5, 6, 7(n) , 8(n) (n = 3-6), 9(n) (n = 3, 5), and 10), we were able to grow single crystals. The X-ray analysis of 4(3), 7(3), 8(3), 8(4), 6, 7(5), and 8(5) revealed close contacts between the chalcogen atoms. These chalcogen-chalcogen interactions impose a ribbon-shape arrangement of molecules in 4(3) and a mutual crossing of two perdendicular planes built of 8(4) molecules. For 4(3) we found a close contact (3.28 A) between the pi planes of two neighboring C6H4 rings of different molecules, whereas in 8(4) such a close contact (3.74 A) was due to an intermolecular interaction. Tubular stacking of the macrocyclic rings was found for 7(5) and 8(5) caused by a ladder-type intermolecular chalcogen-chalcogen interaction.     

GaCl3 Promoted one-step α,α-diethynylation and α,α-diethenylation reactions of silyl enol ethers

In the presence of GaCl₃ and 2,6-di(tert-butyl)-4-methylpyridine, α-monosubstituted silyl enol ethers were α,α-diethynylated with a chlorosilylacetylene in one step. An analogous reaction using a silylacetylene gave α,α-diethenylated ketones.     

Synthesis of 5-(4-hydroxyphenyl)-10,15,20-tris[3,5-di(<Emphasis Type="Italic">tert-</Emphasis>butyl)-4-hydroxyphenyl]porphine and 5-(4-palmitoyloxyphenyl)-10,15,20-tris[3,5-di(<Emphasis Type="Italic">tert-</Emphasis>butyl)-4-hydroxyphenyl]porphine and generation of phenoxyl radicals from them

A porphyrin with a lipophilic hydrocarbon substituent, 5-(4-palmitoyloxyphenyl)-10,15,20-tris[3,5-di(tert-butyl)-4-hydroxyphenyl]porphine, was synthesized for the first time by acylation of 5-(4-hydroxyphenyl)-10,15,20-tris[3,5-di(tert-butyl)-4-hydroxyphenyl]porphine. Oxidation of these compounds with PbO₂ in toluene leads to the corresponding phenoxyl radicals. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 800–803, April, 2007.     

Preparation of macrocyclic and ‘C-clamp’ dicarboxylate compounds

Reductive amination of bis-1,3-(aminomethyl)-4,6-diisopropylbenzene with the 4,4″-dicarboxaldehyde of 1,1′:3′,1″-terphenyl-2′-carboxylic acid, sodium salt, afforded a novel macrocyclic dicarboxylate compound in 71% isolated yield. Purification was effected by filtration in a single step. The synthesis and characterization of two new ‘C-clamp’ compounds, which also contain two m-terphenyl carboxylates but exhibit much greater degree of flexibility, are also described. These compounds are of interest as potential ligands or for host-guest chemistry.     

Unusual synthesis,structure, and thermochromic properties of novel sterically hindered cyclohexadienes

Oxidation of 4-[-morpholino--(2-hydroxyphenyl)]methyl-2,6-di-(tert-butyl)-phenol (I) follows an unusual course, with formal loss of the benzyl carbon atom, to give 2,6-di(tert-butyl)-4-morpholino-4-(2-hydroxyphenyl)cyclohexa-2,5-dienone (II), which is thermochromic in solution. This property is due to the dissociation of (II) into morpholine and 3,5-di(tert-butyl)-2,4-diphenoxyquinone. The structure of (II) was established directly by x-ray diffraction, which enabled its conformational features to be related to its thermochromic properties. An x-ray examination of 3,3,5,5-tetra(tertbutyl)-2,4-diphenoquinone (X), together with the direct synthesis of the thermochromic analog of (II) (2,6-di(tert-butyl)-4-morpholino-4-[2-hydroxy-3,5-di(tert-butyl)phenyl]cyclohexa-2,5-dienone) (XI) from (X) and morpholine, confirmed the proposed mechanism of thermochromic dissociation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1121–1129, May, 1991.The authors thank V. I. Minkin and A. S. Morkovnik for participating in discussions of this work.     

Remarkable Chichibabin-type cyclotrimerisation of 3-nitrotyrosine, tyrosine and phenylalanine to 3,5-diphenylpyridine derivatives induced by hypochlorous acid

Reaction of 3-nitrotyrosine with HOCl in aqueous phosphate buffer (pH 7.4) leads to a mixture of extractable products, including 3,5-di(4-hydroxy-3-nitrophenyl)pyridine (15% isolated yield) and 3,5-di(4-hydroxy-3-nitrophenyl)-2-(4-hydroxy-3-nitrophenylmethyl)pyridine (3%) arising by a Chichibabin-like pyridine synthesis via N-chloroimine intermediates. Under the same conditions, phenylalanine gives 3,5-diphenylpyridine in 9% isolated yield, while tyrosine leads to 3,5-di(4-hydroxyphenyl)pyridine (3%) and 3-(3-chloro-4-hydroxyphenyl)-5-(4-hydroxyphenyl)pyridine (3%).     

Synthesis and crystal structure of 15α,20α-di(4-hydroxylphenyl)calix[4]pyrroles and 10α,20β-di(4-hydroxylphenyl)calix[4]pyrroles

In the presence of methanesulfonic acid as catalyst, the condensation reactions of 5,5′-dialkyldipyrromethanes with p-hydroxyacetophenone in methanol resulted in a mixture of the unexpected polysubstituted 15α,20α-di(4-hydroxylphenyl)calix[4]pyrroles and the expected 10α,20β-di(4-hydroxylphenyl)calix[4]pyrroles in comparable lower yields. The crystal structures of the new calix[4]pyrroles and their oxyacetate derivatives were successfully determined by X-ray diffraction and the intermolecular interactions in the solid state is briefly discussed.     

Reactions of 1,4-bis(tetrazole)benzenes: formation of long chain alkyl halides

The reactions of 1,4-bis[2-(tributylstannyl)tetrazol-5-yl]benzene with α,ω-dibromoalkanes were carried out in order to synthesise pendant alkyl halide derivatives of the parent bis-tetrazole. This led to the formation of several alkyl halide derivatives, substituted variously at N1 or N2 on the tetrazole ring. The crystal structures of 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (2-N,2-N′), 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (1-N,2-N′) and 1,4-bis[(2-(8-bromooctyl)tetrazol-5-yl)]benzene (2-N,2-N′) are reported. Further discussion involves the structure of 1,4-bis[2-(6-bromohexyl)-2H-tetrazol-5-yl]benzene (2-N,2-N′) previously reported.     

N-(α-Amidoalkyl)benzotriazole-mediated synthesis of β′-amido β-diketones: a general synthetic protocol for N-[β-(3,5-di and 1,3,5-trisubstituted pyrazol-4-yl)alkyl] amides

Various β′-amido-β-diketones were first synthesized with N-(α-amidoalkyl)benzotriazole-mediated amidoalkylation of 1,3-diketones in moderate yields. These intermediates undergo rapid condensation with hydrazines to give the corresponding N-[β-(3,5-di and 1,3,5-trisubstituted pyrazol-4-yl)alkyl]amides.     

Efficient synthesis of 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl (X: NMe2; OMe) by homocoupling of 1-bromo-3,5-di(p-X-phenylethynyl)benzene or by heterocoupling of 3,3′,5,5′-tetraethynylbiphenyl with p-X-phenylbromobenzene with nickel or palladium complexes, respectively

The conjugated 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl derivatives were efficiently obtained by homocoupling of 1-bromo-3,5-di(p-X-phenylethynyl)benzene mediated by zero-valent nickel complexes.The 1-bromo-3,5-di(p-X-phenylethynyl)benzene was previously prepared by heterocoupling between 1-bromo-3,5-di(ethynyl)benzene and p-X-iodobenzene (X: NMe₂; OMe) catalysed by the palladium/copper system in good yield. The necessary 1-bromo-3,5-di(ethynyl)benzene was obtained by heterocoupling between 1,3,5-tribromobenzene and 2-methyl-3-butyn-2-ol catalysed by palladium and successive treatment with sodium hydroxide in dry toluene, in good yield.The same 3,3′,5,5′-tetra(p-X-phenylethynyl)biphenyl (X: NMe₂; OMe) derivatives were alternatively synthesised in highest yield by heterocoupling between 3,3′,5,5′-tetra(ethynyl)biphenyl and p-X-bromobenzene (X: NMe₂; OMe) catalysed by palladium in excellent yields. Previously, 3,3′,5,5′-tetra(ethynyl)biphenyl was obtained in practically quantitative yield by homocoupling of 1-bromo-3,5-di[4-(2-methyl-3-butyn-2-ol)] benzene mediated by the zero-valent nickel complex to the 3,3′,5,5′-tetra{di[4-(2-methyl-3-butyn-2-ol)]}biphenyl followed the treatment with sodium hydroxide.     

Synthesis of tripeptides containing a very crowded α,α-disubstituted glycine with pyridine rings by solid-phase Ugi reaction

Tripeptides containing a novel α,α-disubstituted glycine with two pyridine rings, α,α-di(2-pyridyl)glycine (2Dpy), were synthesized by the solid-phase Ugi reaction using di(2-pyridyl)methanimine attached directly to a Rink amide resin. Thereby, yields of the tripeptides, Z-AA₁-2Dpy-AA₃-OMe (AA₁ and AA₃ = Gly or Aib), were markedly improved, compared with yields by the solution method.     

A galabiose-based two-dimensional scaffold for the synthesis of inhibitors targeting P- and P-antigen binding proteins

A disaccharide scaffold based on galabiose (Galα1-4Gal) was synthesized. Four different acceptors were evaluated in the α-galactosylation and a relationship between the nucleophilicity, yield, and α/β-selectivity was found. The scaffold contains two orthogonal derivatisation sites, i.e. at O-2′ and the anomeric position, and as proof of concept, one derivatised galabioside was synthesized. Compounds based on this galabiose-scaffold are potential inhibitors of P- and P^k-antigen binding proteins.     

Convenient synthesis of tridentate 2,6-di(pyrazol-1-yl)-4-carboxypyridine and tetradentate 6,6′-di(pyrazol-1-yl)-4,4′-dicarboxy-2,2′-bipyridine ligands

Citrazinic acid is used as a convenient starting material for both tridentate 2,6-di(pyrazol-1-yl)-pyridine and tetradentate 6,6′-di(pyrazol-1-yl)-2,2′-bipyridine ligands containing carboxylic groups useful for further anchoring of sensitizer on TiO₂ for dye-sensitized solar cells (DSCs). Using 2,6-dichloro-4-carboxypyridine, the synthesis of the terdentate ligands was improved compared to previously used 2,6-dibromo-4-carboxypyridine or 2,6-dichloro-4-ethylcarboxylate pyridine. Controlling the reaction conditions, it is possible to efficiently obtain the monosubstituted 2-chloro-6-pyrazol-1-yl-4-carboxypyridine, a key intermediate for the preparation of tetradentate 6,6′-di(pyrazol-1-yl)-4,4′-dicarboxy-2,2′-bipyridine ligand.     

Synthesis of Derivatives of of Δ2-Imidazolin-5-one and Imidazolidine Containing Residues of Sterically-hindered Phenols

1-Substituted 4-benzylidene-2-{-[3,5-di(tert-butyl)-4-hydroxyphenyl]vinyl}-4-benzylidene-²-imidazolin-5-ones have been synthesized by the interaction of azomethines and N-acylhydrazones (derivatives of 3,5-di(tert-butyl)-4-hydroxybenzaldehyde) with 4-benzylidene-2-methyloxazol-5-one. The acylation of 1,2-bis[3,5-di(tert-butyl)-4-hydroxybenzylideneamino]ethane with acid chlorides in acetonitrile in the presence of triethylamine leads to 1,3-diacyl-2-[3,5-di(tert-butyl)-4-hydroxyphenyl]imidazolidine.     

Kinetic control in the formation of meso-dithia[3.3]-paracyclophane S,S′-dioxide

meso-(R,S)-Dithia[3.3]-paracyclophane S,S′-dioxide is formed with complete stereoselection by the thermolysis of 3,3′-[1,4-phenylene-bis(methylenesulfinyl)]-dipropanoate—that generates in situ two transient sulfenic acid functions—in the presence of p-diethynylbenzene. By employing an improved procedure that we have recently optimized, the title compound has been prepared in a 70% yield as a single diastereoisomer. A density functional B3LYP/6-311+G(d,p) study demonstrates that the final syn-addition cyclization step takes place under kinetic control, through a five-membered transition state that defines the stereochemistry of the resulting cyclophane.