Squaramide
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 the two OH groups are replaced by NH2 groups. 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