We reveal a route for the preparation of phosphinated bisphenol, 1,1-bis(4-hydroxyphenyl)-1-(6-oxido-6H-dibenz < c,e > < 1,2 > oxaphosphorin-6-yl)ethane (2), via a one-pot reaction of 1,1,1-tris(4-hydroxyphenyl)ethane and 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) in the catalysis of p-toluenesulfonic acid. A two-step reaction mechanism, acid-fragmentation of 1,1,1-tris(4-hydroxyphenyl)ethane followed by nucleophilic addition of DOPO, is proposed for the synthesis. Based on (2), a dicyanate ester derivative, 1,1-bis(4-cyanatophenyl)-1-(6-oxido-6H-dibenz < c,e > < 1,2 > oxaphosphorin-6-yl)ethane (3) was prepared and co-cured with a commercially available dicyanate ester, the dicyanate ester of bisphenol A (BACY). Experimental data show that incorporating (3) into BACY enhances the flame retardancy and dielectric properties with little penalty to the thermal properties. A thermoset with T(g) 274 degrees C, coefficient of thermal expansion (CTE) 49 ppm/degrees C, D(k) 3.04 (1 GHz), T(d) (5%,) N(2): 435 degrees C, air: 424 degrees C, and UL-94 V-0 rating can be achieved via this approach. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4851-4860, 2011