Spiropyrans and spirooxazines 5. Synthesis of photochromic 8-(4,5-diphenyl-1,3-oxazol-2-y1)-substituted spiro[indoline-benzopyrans]

Abstract

Photochromic spiro[indoline benzopyrans] containing 4,5 diphenyloxazolyl group at position 8 of the benzopyran fragment have been obtained. New diphenyloxazolyl substituted spiropyrans manifest considerably higher thermal stability of the merocyanine isomers than their naphthopyran analogs.The synthesis and studies of new efficient photochro mic systems, prospective for development of polyfunc tional materials for molecular electronics on their basis, is an actual problem. 2,3 Among the most well known classes of photochromic compounds, spiropyrans are of particu lar interest since, depending on molecular structures, they manifest spectro kinetic characteristics varying in a wide range, as well as due to the relative easiness of their synthesis. 3-5Mechanism of photochromic transformations of spiro pyrans (SPP) (Scheme 1) includes the thermally and photochemically reversible process of heterolytic cleavage Scheme 1 of the C Sp -O bond of the cyclic isomer A with subse quent cis-trans isomerization to the metastable mero cyanine form B. 3-5On the basis of SPP by introduction of the corre sponding functional fragments, it is possible to obtain polyfunctional molecular systems displaying, along with photochromism, fluorescent, 6 magnetic, 7 and complex forming properties switching by optical irradiation. 8 Earlier, 9 we reported on the synthesis of photochromic 5´ (4,5 diphenyl 1,3 oxazol 2 yl) substituted spiro[indoline naphthopyran], the merocyanine form of which reversibly forms complexes with bivalent cations of heavy metals. In continuation of this research, the present work deals with the synthesis and description of photochromic properties of a number of spirobenzopyrans containing diphenyl oxazolyl group at position 8 of the benzopyran fragment. Results and DiscussionThere are two general methods for the synthesis of SPP. The first of them (method I) includes a condensation of corresponding heterocyclic cations with o hydroxy aromatic aldehydes in acidic medium, isolation of salts of o hydroxystyryl derivatives, and spirocyclization of the latter under the action of a base. Method II, used the most often for the preparation of indoline SPP, consists in condensation of a methylene base (or the correspond ing heterocyclic immonium salt in the presence of a base) with o hydroxyaromatic aldehydes. Both methods have been used for the synthesis of indoline SPP containing diphenyloxazolyl substituent (Scheme 2).

Organic photoresponse materials and devices

“…By chemical modification of the molecules these properties can be improved. 165,166 2.1.3.3 Diarylethenes. Diarylethenes are a class of compounds that have aromatic groups bonded to each end of a carbon-carbon double bond.…”

Photochromic and thermochromic spiranes. 34.* synthesis of photochromic 5-(4,5-diphenyl-1,3-oxazol-2-yl)-substituted spirobenzochromeneindolines

“…The sodium salt of the acid 6a, the desyl chloride 7, and the 3H-indolium salts 2a-d were obtained by the previously described methods [16,[21][22][23][24][25].…”

“…In the case of 2-(hydroxyaryl)-4,5-diphenyl-1,3-oxazoles, the method of production of the desyl esters by the alkylation of the salts of the corresponding carboxylic acids with desyl chloride under the conditions of phase-transfer catalysis is preferred [15,16].…”