New condensed indoline bis-spiropyrans

Abstract

For some time, bis-spiropyrans prove to have been at the center of attention of organic chemists. The reason for this is the significant increase in the chain of conjugation for possible opening simultaneously of two pyran fragments, as a result of which a strong bathochromic shift of the absorption band of the photoinduced form [1] must be observed. The introduction of indole fragments into bis-spiropyrans must also assist an increase in the conjugation chain on simultaneously opening two pyran rings. The synthesis of bis-spiropyrans was carried out by the interaction of aromatic o-hydroxy aldehydes with ketones [1], and spiropyrans are obtained by condensation of methylene bases with o-hydroxy aromatic aldehydes [1]. With the aim of obtaining new systems of bis-spiropyrans containing indole fragments, and developing a general method of obtaining isomeric indole bis-spiropyrans, we have studied the condensation of bisanalogs of methylene bases with salicylic aldehydes. Previously in letters [2, 3], we reported the synthesis of new bisanalogs of dimethylidenehexahydroindolo[4,5-e]indole and dimethylidenehexahydrodipyrrolo[1,2,3-d,e;3,2,1-i,j]benzo[g]quinoxa- line Fischer's bases and bis-spiropyran compounds based on them. In the present work, we describe a method for obtaining a new indole bis-spiro compound from the bismethylene base of dimethylidenehexahydro-indolo[7,6-g]indole and propose general three stages synthesis of new condensed indoline bis-spiropyrans based on hexamethyldihydrodipyrrolonaphthalenes 1-3 [4-6].