Pyrex filtered sunlight irradiation of an acetic anhydride of 3,3'-diamino-2,2'-bi-1,4-napthoquinonyl unexpectedly led to the formation of 3',3':N,N-bi[3-amino-2,2'-bi-1,4-napthoquinonyl] which contains only two secondary amino groups. The structure of the photoproduct was elucidated from a FAB mass spectrometric as well as H-1 and C-13 n.m.r. study.