Squaramide is the organic compound with the formula O2C4(NH2)2. Not an amide in the usual sense, it is a derivative of squaric acid wherein two OH centers are replaced by NH2. Squaramides refer to a large class of derivatives wherein some of the H's are replaced by organic substituents. Exploiting their rigid planar structures, these compounds are of interest as hydrogen-bond donors in supramolecular chemistry and organocatalysis. Squaramides exhibit 10-50x greater affinity for halides than do thioureas. Squaramide is prepared by ammonolysis of diesters of squaric acid: O2C4(OEt)2 + 2 NH3 → O2C4(NH2)2 + 2 EtOH N-Substituted squaramides are prepared similarly, using amines in place of ammonia. References Ketones Enamines Cyclobutenes