PHENYLCYCLOBUTADIENOQUINONE

Abstract

No authentic cylobutadiene derivatives appear to have yet been prepared except for biphenylene and related substances, where the four-membered rings are part of fused-ring system. The failure to detect cyclobutadiene or its non-fused ring derivatives among the products of appropriate synthetic reactions can be ascribed either to excessive ring strain or unfavorable electronic configurations. Strong evidence that ring strain is not the
\nmost important factor is now provided by a synthesis of the quite stable (phenylcyclobutadienoquinone (phenylcyclobutendione, I) which to a first approximation is expected to have the same degree of ring strain as phenylcyclobutadiene.