Synthesis of the Substituted 3‐Cyclobutene‐1,2‐diones

Abstract A convenient synthesis of the novel squaric acid derivatives is reported. Unsymmetrically substituted 3,4‐diamino‐3‐cyclobutene‐1,2‐diones and 3‐amino‐4‐hydroxy‐3‐cyclobutene‐1,2‐diones were prepared by interaction of diethyl squarate with different nucleophilic reagents such as alkali, primary and secondary amines and amino acids. Substituted 3‐amino‐4‐aryl‐3‐cyclobutene‐1,2‐diones were synthesized by interaction of squaryl dichloride with different arenes followed by arylsquarylation of amines. Efficient procedures were developed for consequent substitution of ethoxy groups in diethyl squarate and chlorine atoms in squaryl dichloride. The synthesized compounds have a great potential of bioactivity and are useful objects for biomedicinal screening.