L. S. Liebeskind, Marvin S. Yu, R. H. Yu
Oct 1, 1993
Citations
0
Influential Citations
31
Citations
Journal
Journal of the American Chemical Society
Abstract
4,4'-Bi(cyclobutene-1,2-diones), novel compounds derived from squaric acid, here named bisquaryls, were prepared for the first time either by the palladium-catalyzed oxidative dimerization of (tri-n-butylstannyl)cyclobutene-1,2-diones (providing symmetrically substituted bisquaryls) or by a palladium-copper cocatalyzed cross-coupling of 3-substituted-4-(tri-n-butylstannyl)-3-cyclobutene-1,2-diones with 3-halo-4-substituted-3-cyclobutene-1,2-diones (providing a route to unsymmetrically substituted bisquaryls). The novel parent bisquaric acid is a very strong BrOnsted acid that apparently fully ionizes on dissolution; only one pK a value (pK a = -4.49) was observed