A few novel methods were developed for the regioselective preparation of p-hydroxybenzoic acid (pHBA) and its amino derivative by means of the Kolbe–Schmitt reaction. Thus, the carboxylation of tetraalkylammonium phenoxide at 125 °C under the CO2 pressure of 5.0 MPa in the presence of K2CO3 gave pHBA in a maximum yield of 56% with the regioselectivity of 97–100%. The carboxylation of potassium phenoxide (PhOK) at 230 °C under the CO2 pressure of 0.5 MPa also gave pHBA regioselectively in a 39% yield, together with unaltered phenol (61%). Under such conditions, the potassium salt of salicylic acid (SA) once formed was transformed into pHBA. Heat treatment of the dipotassium salt of 13C labeled SA indicated that the transformation occurs via two pathways, i.e., the intramolecular rearrangement of the salicylate (66%) and the decarboxylation of the salicylate followed by the recarboxylation of the resulting PhOK (34%). Furthermore, the carboxylation of cesium m-aminophenoxide and 5-amino-1-naphthoxide with CO2 gave regioselectively 4-hydroxyanthranilic and 8-amino-4-hydroxy-1-naphthoic acids, respectively, in good yields. This is a simple one-pot reaction giving these industrially useful acids with good yields.
An aminophenol ether having the formula ##STR1## is produced by reacting an alkali aminophenolate having the formula ##STR2## wherein M represents an alkali metal atom; with an organic halide having the formula R-X wherein R represents a lower alkyl group, a lower alkenyl group or benzyl group; and X represents a halogen atom in substantially anhydrous condition in the presence of an alkali metal hydroxide and a quaternary salt selected from the group consisting of quaternary ammonium salts and quaternary phosphonium salts.
In one embodiment this invention provides injection moldable polyimides, as exemplified by the condensation and imidization product of a aromatic dianhydride such as 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride with a novel aromatic diamine such as 2,2-bis[p,p'-(m-aminophenoxy)phenylsulfonyl(p-phenyleneoxy)phenyl]propane.
In one embodiment this invention provides novel thermosetting aromatic polyimide prepolymers which have superior solubility and flow properties, and which can be thermally cured to heat and oxidation resistant thermoset adhesives, films and molded products. Illustrative of a prepolymer is the dimaleimide of 2,2-bis[p,p'-(m-aminophenoxy)phenylsulfonyl(p-phenyleneoxy)-phenyl]propane .
Room‐Temperature Ionic Liquid–Promoted Williamson's Synthesis of Ethers: A Facile Synthesis of Diaryloxymethanes
作者:S. V. More、S. S. Ardhapure、N. H. Naik、S. R. Bhusare、W. N. Jadhav、R. P. Pawar
DOI:10.1080/00397910500281267
日期:2005.12.1
A simple and efficient method has been developed for the synthesis of phenolic ethers using room-temperature ionic liquid, not only as solvent but also as promoter. Ionic liquid was recycled and subsequently reused without any loss of the product.