This invention describes resins with phosphate cores and a simple, three-step process for their synthesis. Preferred resins are cyanate ester resins with bridging phosphate groups. These resins can be cured to produce thermoset polymers having Tgs of between 131 and >360° C. depending on the number of cyanate ester groups per phosphate and the substitution pattern of the aromatic rings. The high char yields of these resins, up to about 67%, coupled with the phosphate core means that these materials will have applications as fire-resistant polymers. Additionally, these materials can potentially be blended with conventional cyanate esters or other compatible thermosetting resins to improve the fire resistance of composite materials. Other applications may include use in fire-resistant circuit boards, or as surface coatings to reduce flammability of conventional composite materials or thermoplastics.