One‐Pot Alkoxylation of Phenols with Urea and 1,2‐Glycols

Abstract

A one-pot epoxide-free alkoxylation process has been developed for phenolic compounds. The process involves heating phenols and urea in 1,2-glycols at 170-190°C using Na 2 CO 3 /ZnO as co-catalysts under atmospheric conditions. During the course of this new alkoxylation reaction, a five-membered ring cyclic carbonate intermediate, ethylene carbonate (EC) or propylene carbonate (PPC), was produced in-transit as the key intermediate and was subsequently consumed by phenols to form alkoxylated ether alcohols as final products in excellent yields. For instance, phenol, bisphenol A (BPA), hydroquinone and resorcinol were converted into their respective mono-alkoxylated ether alcohols on each of their phenolic groups in 80-95% isolated yields. In propoxylation of phenols, this approach shows great product selectivity favoring production of high secondary alcohols over primary alcohols in isomeric ratios of nearing 95/5. Since ammonia (NH 3 ) and carbon dioxide (CO 2 ) evolving from the reaction can be re-combined in theory into urea for re-use, the overall net-alkoxylation by this approach can be regarded as a simple condensation reaction of phenols with 1,2-glycols giving off water as its by-product. This one-pot process is simple, safe and environmentally friendlier than the conventional alkoxylated processes based on ethylene oxide (EO) or propylene oxide (PO). Moreover, this process is particularly well-suited for making short chain-length alkoxyether alcohols of phenols.

A Facile Synthetic Route to Ether Diols Derived from 1,1-Cyclopentylenylbisphenol for Robust Cardo-Type Polyurethanes

“…Because phenolic hydroxyl groups are slightly acidic in nature and far less reactive toward isocyanates than primary or secondary hydroxyl groups of alkyl alcohols, alkoxylation of C0 to produce short-alkoxylated derivatives was performed to produce diols for use in PU applications. , These alkoxylation reactions were done by reacting C0 with ethylene carbonate (EC) or propylene carbonate (PPC) at 160–180 °C for producing the respective ethoxylated or propoxylated diols, and the spectra of recrystallized products, C1 and C2, are shown in Figures S2 and S3, respectively.…”

Synthesis and evaluation of alkoxylated-ether diols of hydroquinone with different chain-lengths as extenders in segmented polyurethanes

“…The minor isomeric products of HQPP are assumed to be the isomers with one or two primary alcohols. [26] The reason for the mixed-product formation can be readily explained since there are two possible reaction sites on the propylene carbonate ring. The attacking of phenols on the carbon without the methyl-substituted site of propylene carbonate is preferentially favoured due to less steric hindrance.…”