Mitsunobu reactions of aliphatic alcohols and bulky phenols

Alkylation of hydrazinedicarboxylate (a Mitsunobu by-product) is not a notable problem in common Mitsunobu alkyl aryl etherification reactions. Good yields can be obtained with a wide range of solvents. However, this side reaction can cause yield reduction for the reactions of sterically hindered phenols and primary alcohols. To suppress the side reaction, solvent effect was investigated. It was found that hydrazinedicarboxylate is about five times less soluble in diethyl ether than in THF, and the yields are improved for ortho-substituted phenols of a wide range of steric hindrance using diethyl ether as the solvent instead of THF which is the more commonly used for Mitsunobu reactions.     

Facile O-arylation of phenols and carboxylic acids

[reaction: see text] A facile, transition-metal-free O-arylation procedure for phenols and aromatic carboxylic acids has been developed that affords good to excellent yields of arylated products under very mild reaction conditions. A methoxy-substituted aryl triflate affords O-arylated products in high yields with excellent regioselectivity. This chemistry tolerates a variety of functional groups.     

Ligand-free copper-catalyzed O-arylation of nitroarenes with phenols

The first example of ligand-free copper-catalyzed O-arylation of nitroarenes with phenols was developed, achieving unsymmetrical diaryl ethers in moderate to excellent yields. This arylation proceeded smoothly without promotion of the ligands, and displayed great functional group compatibility. Thus, the method represents a new, facile, and cost-effective approach to access unsymmetrical diaryl ethers.     

Cu-catalyzed N- and O-arylation of 2-, 3-, and 4-hydroxypyridines and hydroxyquinolines

With use of Cu-based catalysts, 2- and 4-hydroxypyridines were N-arylated in modest to excellent yields. In the case of 2-hydroxypyridine, the use of 4,7-dimethoxy-1,10-phenanthroline, 3, expanded the scope of previous literature reports to include the use of N-containing heteroaryl halides, and 2-substituted aryl halides. In addition, by using a copper catalyst based on 2,2,6,6-tetramethylheptane-3,5-dione, 4, the first N-arylations of 4-hydroxypyridines and O-arylations of 3-hydroxypyridines with aryl bromides and iodides have been accomplished. [reaction: see text].     

Cu-nanoparticle catalyzed O-arylation of phenols with aryl halides via Ullmann coupling

Recyclable Cu-nanoparticles provide an efficient, economic, and novel method for the synthesis of diaryl ethers via Ullmann type coupling. This method provides a wide range of substrate applicability and avoids the use of a heavy metal co-catalyst and gives diaryl ethers in satisfactory yields.     

Enantioselective Cu-catalyzed conjugate addition of diethylzinc to acyclic aliphatic enones

[reaction: see text] A new P-chiral phosphine bis(sulfonamide) ligand has been developed that allows the Cu-catalyzed enantioselective conjugate addition of Et(2)Zn to acyclic aliphatic enones. The reactions proceed with excellent levels of enantioselectivity (90-95% ee) with a range of enone substrates, involve the use of only 1.2 equiv of Et(2)Zn, and give best results at ambient temperature.     

Dipole relaxation in normal aliphatic alcohols

A new mechanism of dipole relaxation and molecular motion in normal aliphatic alcohols is suggested, based on the assumption of the existence of consequent reorientations of the molecules in chains It is shown that the experimental data obtained by different methods of dielectric spectroscopy, including TDS. can be described accurately within the framework of the model.     

Graphite oxide-catalyzed acetylation of alcohols and phenols

Graphite oxide (GO) was used as a catalyst for the reactions of alcohols and phenols with acetic anhydride. The acetates of primary and secondary alcohols were prepared in good to excellent yields in short reaction time under mild conditions. Electron deficient phenols could be converted to the corresponding acetates steadily. As an efficient catalyst, GO is easily available, cheap, moderately toxic and weakly acidic.     

Impregnated copper on magnetite as catalyst for the O-arylation of phenols with aryl halides简

Nanoparticle Fe304 encapsulated CuO, as a heterogeneous catalyst, is a facile system for the synthesis of diaryl ethers by the cross-coupling reaction of various substituted aryl halides with various substituted phenols, which avoids using any type of expensive ligand and can be recovered from the reaction mixture by using a simple magnet. Moreover, this catalyst can be reused three times with high catalytic activity.     

Chemoselectivity in the microwave-assisted solvent-free solid-liquid phase benzylation of phenols: O- versus C-alkylation

The outcome of the solvent-free benzylation of phenol and 4-substituted phenols (such as 4-cresol and 4-chlorophenol) under MW irradiation was found to depend on the absence or presence of the base (K₂CO₃) and catalyst (triethylbenzylammonium chloride (TEBAC)). Reaction of benzyl halides at 80-120 °C in the presence of K₂CO₃ and TEBAC resulted in O-alkylation in high (89-96%) chemoselectivities. In the absence of TEBAC, the proportion of C-alkylation was considerable (16-34%). Omitting also K₂CO₃ from the reaction mixture, C-alkylation became predominant. In the case of 4-tert-butylphenol, the presence of TEBAC promoted C-alkylation. The selectivity of the alkylations can be fine-tuned by choosing the appropriate conditions.     

Glyoxal bis(phenylhydrazone) as promoter for CuI-catalyzed O-arylation of phenols with bromoarenes

A very simple bishydrazone-type ligand, glyoxal bis(phenylhydrazone) (L1), was found to effectively promote the CuI-catalyzed O-arylation of phenols with aryl bromides. This cross-coupling reaction proceeded in acetonitrile at 60-80 °C in the presence of K₃PO₄ as base. A diverse array of phenols and bromoarenes was employed as substrates to afford diaryl ethers in good to excellent yields, and some base-sensitive groups, such as ester, aldehyde, and ketone groups, can survive under the mild reaction conditions.     

Cu-catalyzed asymmetric conjugate additions of alkylzinc reagents to acyclic aliphatic enones

Cu-catalyzed enantioselective conjugate additions to acyclic aliphatic enones are reported. The resulting enolates may be functionalized intra- and intermolecularly, leading to the formation of an additional C-C bond. The utility of the present method is not limited to reactions involving Et2Zn; a variety of alkylzincs may be used. Moreover, many of the requisite substrates can be easily accessed through catalytic olefin cross metathesis.     

Gal3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was catalyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.     

Condensation of phenols and alcohols with 1,2-dichloroethyl-gem-dichlorocyclopropanes

Dichlorocarbenation of 3,4-dichlorobut-1-ene by Makosza method results in the stereoisomeric 1,2-dichloroethyl-gem-dichlorocyclopropanes in a 1:1 ratio. The reaction of the mixture of stereoisomeric gem-dichlorocyclopropanes with phenols and alcohols in dimethylsulfoxide in the presence of solid sodium hydroxide gives rise to the corresponding ketals containing the exocyclic double and triple bonds. In this case, the acetylene compounds dominate in the reaction products. The ratio of the reaction products containing the double and triple bonds depends on the nucleophile nature.     

Direct synthesis of enaminone functionalized biaryl ethers by CuI-catalyzed O-arylation of enaminone functionalized phenols

The O-arylation of o-enaminone functionalized phenols, namely, (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-ones, has been achieved via a self-promoted process in the presence of CuI, which provided a class of new biaryl ethers bearing a reactive enaminone fragment. The reactions were performed under mild conditions and the functionalized biaryl ether products have been found as useful building blocks for the assembly of heterocyclic compounds.     

Intramolecular O-arylation of phenols with phenylboronic acids: application to the synthesis of macrocyclic metalloproteinase inhibitors

[reaction: see text]. The copper acetate mediated intramolecular O-arylation of phenols with phenylboronic acid pseudopeptides is the key step in the preparation of macrocyclic biphenyl ether hydroxamic acid inhibitors of collagenase 1 and gelatinases A and B. The intramolecular macrocyclization was found to be mild and tolerant of common chemical functionality. This methodology should provide a general route to macrocyclic biphenyl ethers.