The synthesis of some 4,4′‐disubstituted‐2,2′‐biquinolines

2,2′‐Biquinoline dioxide and 4,4′‐dichloro‐2,2′‐biquinoline have been used for the preparation of the following 4,4′‐disubstituted‐2,2′‐biquinolines: dimethoxy, diethoxy, dihydroxy, dipiperidino, dipyrrolidino, dibromo, diphenoxy, dithiophenoxy, di( p ‐chloro‐phenoxy), di( p ‐bromophenoxy), di( p ‐fluorophenoxy), di(β‐naphthoxy) and the dinitro dioxide. Molar extinction coefficients have been determined for several of the copper (I) complexes of these compounds.