Squarylium compounds of the formula:
 wherein Q¹ and Q² are each independently a pyrylium, thiopyrylium, selenopyrylium, benzpyrylium, benzthiopyrylium or benzselenopyrylium nucleus, and R¹ and R² are each independently an aliphatic or cycloaliphatic group, can be prepared by reacting a squaric acid derivative of the formula:
 with a compound of the formula Q²CH₂R² in the presence of a base. The derivatives of Formula II may be prepared by condensing a 2,3,4,4-tetrahalocyclobut-2-en-1-one with a compound of the formula Q¹CH₂R¹ in the presence of a base to produce a compound of the formula:
 wherein Q¹ and R¹ are as defined above, and X represents chlorine or bromine, and hydrolyzing the compound of Formula III. Alternatively, the derivatives of Formula II may be prepared by reacting a diester, monoacid chloride monoester or diacid chloride of squaric acid with a compound of the formula Q¹CH₂R¹ in the presence of a base, followed by hydrolysis of the resultant monoacid chloride or monoester derivative of the compound of Formula II to the parent compound.
                            式中的鳞片状化合物:
 其中 Q¹ 和 Q² 各自独立地为
吡喃鎓、
硫吡喃鎓、
硒吡喃鎓、苯并
吡喃鎓、苯
硫吡喃鎓或苯并
硒吡喃鎓原子核,R¹ 和 R² 各自独立地为脂肪族或环脂族基团:
 与式 Q²CH₂R² 的化合物在碱存在下反应,可制备式 II 衍
生物。式 II 衍
生物可通过在碱存在下将 2,
3,4,4-四卤
环丁-2-烯-1-酮与式 Q¹CH₂R¹ 的化合物缩合生成式的化合物来制备:
 其中 Q¹ 和 R¹ 如上所定义,X 代表
氯或
溴,然后
水解式 III 的化合物。另外,式 II 衍
生物的制备方法是:在碱存在下,将角鲨酸的二酯、单酰
氯单酯或二酰
氯与式 Q¹CH₂R¹ 的化合物反应,然后将得到的式 II 化合物的单酰
氯或单酯衍
生物水解为母体化合物。