Squaramide

Squaramides are amides of squaric acids. They are four membered vinylogously conjugated diamides. Hydrogen bonding occurs at four locations and is aided by delocalisation of electrons on Nitrogen's orbitals to the carbonyl group. H-bonding and thus delocalisation further increases ring aromaticity.^[1]

References

1. Chem. Soc. Rev., 2011, 40, 2330/2346