Practical and high yielding routes to substituted cyclobutenediones are described. 3, 4-Bis (l- methyleth-oxy) cyclobut-3-ene-l, 2-dione (diisopropyl squarate), a stable, crystalline derivative of squaric acid, was easily prepared by refluxing squaric acid in 2- propanol/benzene with azeotropic removal of HzO. Reaction with organolithium reagents proceeded in very high yield to give stable, isolable 1, 2-adducts. Treatment in a two- ...
