REACTION OF A QUINONE METHIDE WITH TRIETHYL PHOSPHITE

Quinone methide (1) reacts with triethyl phosphite in n-heptane or benzene solution at 25-30° to form bisphenol (2) (65-75%), a trimer tentatively identified as trisphenol (3) (12-17%), phosphonate (4) (2-5%), and minor by-products. The phosphite functions as a true catalyst for the unusual carbon-carbon condensations leading to 2 and 3, and rate measurements show that the disappearance of 1 follows strict second-order kinetics (first order in 1, first order in phosphite). In the presence of ethanol, phosphonate 4 becomes the principal product, while in the presence of benzaldehyde equivalent amounts of triethyl phosphate and stilbenol (20) are formed in a major competing process. The immediate precursor of bisphenol 2 is shown to be quinone methide (11), whose rearrangement to 2 can be accelerated by carrying out the reaction in the presence of triethylamine. On the basis of these data and other facts, it is shown that the reaction of 1 with triethyl phosphite can be rationalized by a mechanism involving ylides (8 and 12) as key intermediates. Addition of 8 or 12 to 1, followed by prototropic rearrangements and loss of triethyl phosphite, accounts for the formation of bisphenol 2 and trisphenol 3, respectively. © 1969, American Chemical Society. All rights reserved.