Diarylmethyl ethers and Pd salts or complexes: a perfect combination for the protection and deprotection of alcohols

Primary and secondary alcohols are easily protected as diphenylmethyl (DPM) or bis(methoxyphenyl)methyl (BMPM) ethers in good yield using PdCl₂(CH₃CN)₂ as catalyst in dichloroethane at 60 or 20 °C, respectively. These conditions are compatible with other functional and protecting groups such as halides, esters, acetal, benzyl, para-methoxybenzyl, benzyloxycarbonyl, and tert-butyldiphenylsilyl. Good selectivity was observed in favor of primary over secondary alcohols. Deprotection of diphenylmethyl or bis(4-methoxyphenyl)methyl ethers was efficiently achieved at room temperature using PdCl₂(CH₃CN)₂ in dichloroethane in the presence of 10 equiv of ethanol.     

PdCl2, a useful catalyst for protection of alcohols as diphenylmethyl (DPM) ethers

Primary, secondary, benzylic and allylic alcohols are efficiently converted to the corresponding diphenylmethyl ethers in the presence of catalytic amounts of PdCl₂.     

O-diphenylmethylation of alcohols and carboxylic acids using diphenylmethyl diphenyl phosphate as alkylating agent

Diphenylmethyl diphenyl phosphate reacts quickly under mild conditions with various alcohols and carboxylic acids towards diphenylmethyl ethers and esters respectively while hydroxyacids can be selectively alkylated at the alcohol site.     

High yield protection of alcohols, including tertiary and base sensitive alcohols, as benzhydryl ethers by heating with diphenyldiazomethane in the absence of any other reagent

A protecting group that can be introduced efficiently without the need for any acid or base catalysis and which is not prone to acid or base catalysed migration is a significant advantage for many syntheses. Benzhydryl [diphenylmethyl] ethers of sugar lactones are formed in high yield under neutral conditions when the corresponding alcohol is heated with diphenyldiazomethane in an inert solvent such as acetonitrile or toluene; this allows the easy protection of base sensitive and highly hindered tertiary alcohols in the absence of any other reagents.     

Facile synthesis of diphenylmethyl esters from 2-diphenylmethoxypyridine using catalytic boron trifluoride·diethyl etherate

A practical method for the direct preparation of diphenylmethyl (DPM) esters from 2-diphenylmethoxypyridine is described. The reaction was readily performed in the presence of a catalytic amount of boron trifluoride-diethyl etherate at room temperature. Using this reaction protocol, various carboxylic acids were converted to DPM esters with high yields. This method is highly effective for the protection of carboxylic acids and the synthesis of DPM esters, and offers a promising approach for facile esterification of a variety of carboxylic acids.     

EFFECTS OF VINYL ETHERS UPON RADICAL POLYMERIZATIONS

Various vinyl ethers have been examined as additives during radical polymerizations initiated by azobisisobutyronitrile at 60°C; the monomers were methyl methacrylate (MMA), styrene (STY) and acrylonitrile (AN). For MMA and STY, the vinyl ethers were incorporated to only small extents but they caused reductions in rate of polymerization and chain length of the resulting polymer; the effects can be attributed to the low reactivities in growth reactions of radicals to which a vinyl ether unit was last added. Copolymerization of the vinyl ethers with AN was more evident but, in many cases, it was accompanied by increased rate of consumption of AN and increased chain length of the polymer. These changes can be explained in terms of a physical effect which can be likened to that believed to be responsible for the gel effect. It is considered that polymer radicals are rather tightly coiled in an indifferent solvent so that the normal bimolecular termination is impeded.     

Protic ionic liquids as recyclable solvents for the acid catalysed synthesis of diphenylmethyl thioethers

The acid catalysed formation of diphenylmethyl (DPM) thioethers was successfully achieved using the protic ionic liquid (pIL) triethylamine:methanesulfonic acid (TeaMs) as the reaction solvent under microwave irradiation. A slight excess of methanesulfonic acid (10% v/v) was required to facilitate the reaction, which was applied to a variety of thiols. Aliphatic, aromatic and heterocyclic aromatic thiols were converted to their corresponding DPM thioethers in high yields (63–99%), in short reaction times (5–20 min) and using mild temperatures (80–100 °C). Finally, the pIL (TeaMS) was recycled five times without loss of yield.     

腙型双冠醚对碱金属的配位性能

本文报道了五个腙型双冠醚的合成。电导测定结果表明含苯并-15-冠-5单元的双冠醚与四苯基硼酸钾、铷、铯,含苯并-18-冠-6单元的双冠醚与四苯基硼酸铯生成2:1夹心型配合物(冠醚单元:金属离子)。并用这些双冠醚的氯仿溶液萃取苦味酸碱金属盐水溶液,测定了萃取百分率和计算了萃取平衡常数,结果表明腙型双冠醚的萃取能力及选择性优于相应的单冠醚。     

PHOTOPHYSICAL AND PHOTOBIOLOGICAL PROPERTIES OF DIPORPHYRIN ETHERS

Spectral properties of several diporphyrin ethers were assessed in different solvents and after accumulation by leukemia L1210 cells in vitro. To facilitate studies in a variety of solvents, both tetramethylesters of the diporphyrin ethers and free acids were employed. For comparison, studies on the corresponding porphyrin monomers were also carried out. The joining of two porphyrins by an ether linkage had several consequences. We observed a blue shift in the Soret band of the ethers, but not of the corresponding simple porphyrins, in protic solvents. This phenomenon is likely related to ether aggregation under conditions which promote H-bonding. The presence of an ether linkage was associated with enhanced fluorescence at 630-640 nm and decreased fluorescence lifetimes and yields, especially in protic solvents. The ether linkage was unaffected by intracellular enzymes, but porphyrin esters were readily hydrolyzed upon accumulation by L1210 cells. The joining of two hematoporphyrin molecules by an ether linkage promoted dye accumulation by L1210 cells. In contrast, accumulation of mesoporphyrin and protoporphyrin was thereby retarded.     

N,N'-Diisopropyl-O-Diphenylmethyl Isourea: A Mild and Convenient Alkylating Agent for the Formation of Cephalosporin Derivatives

N,N-Diisopropyl-O-diphenylmethyl isourea reacts with cephalosporin-4-carboxylic acid in tetrahydrofuran at room temperature to give the diphenylmethyl (DPM) ester in good yields without isomerization of the double bond from C-3 to C-2.     

烯丙基苯并冠醚的合成

邻苯二酚用溴丙烯单醚化、Claisen重排,得到3-烯丙基和4-烯丙基邻苯二酚。烯丙基邻苯二酚与α,ω-二卤代多缩乙二醇缩合,得到烯丙基苯并冠醚。本文利用这一方法,合成了3-烯丙基苯并15-冠-5和4-烯丙基苯并15-冠-5。其结构通过元素分析、红外光谱、质谱和质子核磁共振谱确认。测定了它们对苦味酸钠和苦味酸钾的络合容量,以及它们作为活性物质的PVC膜离子选择电极的性能。     

氧化偶氮双苯并冠醚的合成

合成了两种新的氧化偶氮双苯并冠醚,改进了氧化偶氮双苯并15-冠-5的制备方法,使其收率提高到65.3%。工作中观察到,电子转移剂的离解程度对产物收率起重要作用,井以溶剂的极性给予解释。对这类双冠醚的光和热异构化做了初步探讨。     

多缩乙二醇二苯醚与甲醛缩聚合成酚醛型聚合物假冠醚的研究

本文采用苯酚、多缩乙二醇二氯化物、多缩乙二醇等为起始原料,合成了九个多缩乙二醇二苯醚新单体,经甲醛聚合获得一系列聚合物假冠醚,并对它们的溶解性能、络合性能以及催化作用等进行研究。     

A new method for the preparation of diphenylmethyl ethers

Various diphenylmethyl ethers are prepared under mild conditions by using tri-diphenylmethyl phosphate as alkylating agent. O-Diphenylmethyl-L(?)-Lactic Acid is prepared by this method.     

DIRECT OXIDATIVE DEPROTECTION OF TETRAHYDROPYRANYL ETHERS USING HEXAMETHYLENETETRAMINE-BROMINE SUPPORTED ONTO SILICA GEL UNDER MICROWAVE IRRADIATION IN SOLVENTLESS SYSTEM

Primary and secondary tetrahydropyranyl ethers (THP ethers) are converted to their corresponding carbonyl compounds efficiently using hexamethylene-tetramine-bromine supported onto silica gel under microwave irradiation in solvent-free conditions.     

羧酸冠醚的合成

羧酸冠醚的合成吴琳，王志林，卞清，张进琪，朱春生（南京大学化学系南京２１００９３）曹建国（盐城师专化学系）关键词冠醚，离子迁移羧酸冠醚环上的羧基，对冠醚环的选择输送金属离子起着协同的作用。近十余年来，将羧酸冠醚选择萃取金属离子的能力应用于金属离子的液...     

酚醛冠醚共缩聚物的合成与性能

用2,6-二羟甲基-4-苯基苯酚分别与二苯并-18-冠-6(2B18C6)、二苯并-24-冠-8(2B24C8)、二苯并-30冠-10(2B30C10)、苯并-15-冠-5(B15C5)、苯并-18-冠-6(B18C6)缩聚合成了五种酚醛型冠醚共聚物。我们用聚冠醚的氯仿溶液萃取苦味酸碱金属盐水溶液,研究了它们对金属离子的络合性能。结果表明,聚冠醚(PB15C5)和(PB18C6)的萃取能力和选择性显著优于相应的单冠醚。     

Jet spectroscopy of arylmethyl radicals in the visible region: assignment of low-frequency vibrational modes in diphenylmethyl and chlorodiphenylmethyl radicals

The D(1)-D(0) transitions of diphenylmethyl (DPM) and chlorodiphenylmethyl (CDPM) radicals were studied by laser induced fluorescence (LIF) spectroscopy in a supersonic jet. Laser induced fluorescence excitation and dispersed fluorescence (DF) spectra were obtained for DPM and CDPM radicals produced by ArF excimer laser (193 nm) photolyses of their chlorides. With the aid of the density functional theory (DFT) calculation, vibronic bands are assigned by comparing the observed LIF excitation spectra of the jet-cooled radicals with the single vibronic level DF spectra. Low-frequency vibrations of 55 and 53 cm(-1) in the ground and excited states, respectively, are assigned to the symmetric phenyl torsional mode of the DPM radical. The geometries of DPM in the ground and excited states are discussed with regards to observed spectra and DFT calculations. Similarly for the CDPM radical, symmetric phenyl torsional and Ph-C-Ph bending modes are assigned and the halogen-substitution effect in equilibrium geometry is discussed.     

苯偶姻醚类对碘鎓盐引发环氧聚硅氧烷光聚合的促进作用

鎓盐引发的阳离子光聚合已有很多报道,但多偏重于低分子量环氧化合物的溶液聚合,对环氧树脂薄膜本体聚合的报道较少。鎓盐在紫外区(>300nm)吸收光的能力很低,苯偶姻醚可促进氟硼酸二苯碘[Ph_2I BF_4~-]在300—400nm的光分解,从而有助于它引     

Synthese deuteriierter Derivate diastereomerer Cyclopentapeptide für die Konformationsanalyse

Synthesis of Deuteriated Derivatives of Diastereomeric Cyclopentapeptides for Use in Conformational Analysis. The syntheses and properties of eight cyclic pentapeptides containing glycine with two deuterium atoms at C(α) (Gly*) are described: cyclo-[-Gly-L -Cys(DPM)-Gly-Gly*-L -Pro-], cyclo-[-Gly*-L -Cys(DPM)-Gly-Gly*-L -Pro-], cyclo-[-Gly-L -Cys-(DPM)-Gly-Gly*-D -Pro-], cyclo-[-Gly*-L -Cys(DPM)-Gly-Gly*-D -Pro-], cyclo-[-Gly-L -Ala-Gly-Gly*-L -Pro-], cyclo-[-Gly*-L -Ala-Gly-Gly*-L -Pro-], cyclo-[-Gly-L -Ala-Gly-Gly*-D -Pro-], and cyclo-[-Gly*-L -Ala-Gly-Gly*-D -Pro-] (DPM = diphenylmethyl). These particular compounds were chosen in order to assign by NMR. unambiguously certain conformational features, like hydrogen-bonding and shielding, to individual peptide bonds.