Photochromic dihetarylethenes. 18. New approach to the synthesis of dithienothiophene and preparation of its photochromic derivative

A new approach to the synthesis of dithienothiophene was developed, and 1,2-bis(2,6-dimethyldithieno[3,2-b;2",3"-d]thiophen-3-yl)hexafluorocyclopent-1-ene was prepared. The latter compound is the first representative of photochromic dihetarylethenes with the fused tricyclic fragments linked through the perfluorocyclene bridge.     

Photochromic dihetarylethenes. 6. Photochromic derivatives of thieno[3,2-b]thiophene

1,2-Bis{5-(2-benzothiazolyl)-2-methyl-6-trifluoromethylthieno[3,2-b]thiophen-3-yl}hexafluorocyclopentene possessing high fatigue resistance was synthesized for the first time. Its photochromic and fluorescence properties were studied. The structure of its cyclic form was established by X-ray diffraction analysis.     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

New approach to the synthesis of 2-carbamoylbenzothiazoles

The reactions of substituted anilines with chloroacetamide and sulfur in the presence of triethylamine afforded monothiooxamides. When treated with K₃Fe(CN)₆, the latter underwent cyclization to form 2-carbamoylbenzothiazoles. The reactions were accompanied by the formation of the corresponding thiooxanilic acids, which also underwent cyclization to form benzothiazole-2-carboxylic acids.     

Photochromic Dihetarylethenes. 12. Synthesis of 5-Alkyl-2-(1,3,4-oxadiazol-2-yl)thiophenes and Their Photochromic Derivatives

Photochromic derivatives of 5-alkyl-2-(1,3,4-oxadiazol-2-yl)thiophenes have been synthesized for the first time. Their photochromic and fluorescent properties have been studied.     

Photochromic dihetarylethenes. 10. Photochromic 1,2-bis[2-(benzothiazol-2-yl)-3-thienyl]- and 1,2-bis[2-(benzothiazol-2-yl)benzothiophen-3-yl]ethenes

Dithienylethenes containing the thiophene rings with benzothiazolyl substituents in position 2 were synthesized. 1,2-Bis[2-(benzothiazol-2-yl)benzothiophen-3-yl]hexafluorocyclopentene and 1,2-bis[2,5-di(benzothiazol-2-yl)-3-thienyl]hexafluorocyclopentene possess photochromic properties. The open forms of 1,2-bis(2-benzothiazolylhetaryl)ethenes fluoresce, but introduction of the benzothiazole rings into dihetarylethenes significantly lowers the fatigue resistance of photochromes and favors thermal reversibility.     

Photochromic dihetarylethenes

The structures of two hetarylethene photochromes,viz., 1,2-bis(2-ethyl-5-ethylsulfonylthien-3-yl)perfluorocyclopentene and 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene, were established by X-ray diffraction analysis. The conformational parameters of the title compounds are considered. The cyclopentene ring in the former compound is planar and this ring in the latter compound adopts an envelope conformation. There are no overall conjugated systems in the molecules under study. In both structures, the dihetaryl fragments are rotated with respect to the perfluorocyclopentene fragments by ∼55°. The thiophene and benzoxazole rings in 1,2-bis[5-(benzoxazol-2-yl)-2-methylthien-3-yl]perfluorocyclopentene are coplanar. For Part 3, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 74–77, January, 2000.     

Photochromic dihetarylethenes

1,2-Bis[2-methyl-5-(benzoxazol-2-yl)thien-3-yl]hexafluorocyclopentene was synthesized, and its photochronic properties were studied For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1011–1014, May, 1999.