Photochromic perfluorocyclopentenes substituents

Examples for the synthesis of photochromic perfluorocyclopentenes 71 and 72 with the dithienothiophene substituents (Scheme 29) are given in works [77a-c]. 

Abstract The review considers the synthesis and structures of photochromic products, in which hetaryl substituents are separated by the centtal 1,2-perfluorocyclopentene moiety. It was also briefly presented main methods for synthesis of octafluorocyclopentene and its reactivity. Among methods used for the synthesis of the photochromes, the reactions of hthium derivatives of thiophene, benzothiophene, and other heterocyclic compounds with octafluorocyclopentene, 1,2-dichlorohexafluorocyclopentene, and their analogues are described. Another general method for the synthesis of dihetarylethenes, considered in the review, is based on the McMurry reaction involving the initial... 

The synthesis and structures of the photochromic products in which the hetaryl substituents are separated by the central 1, 2-perfluorocyclopentene fragment are described in the present review. The first section briefly presents the main methods for the synthesis of perfluorocyclopentene and its reactivity that predetermines methods for the synthesis of photochromic dihetarylethenes. The second section directly deals with the methods for the synthesis of these photochromes, and spe-ciflc features of their structures are described in the third section. The photochromic properties of the products, for minor exceptions, are not considered. 

A novel and efficient palladium-catalyzed direct diheteroarylation of 1,2-dichlorop erfluorocyclopentene with a variety of heteroarenes has recently been reported, giving rise to l,2-di(hetaryl)perfluorocyclopentene photochromic compounds 102. The reaction occurs with thiazoles, thiophenes, or furan derivatives and tolerates varions substituents [112] (Scheme 37). 

Let us begin from the consideration of the structures of photochromic DTE 113A and 37A with substituents in positions 2,2 and 5,5. The numbering of atoms in the heterocycle is shown in Scheme 41 perfluorocyclopentene is denoted as F thiophene cycles are T1 and T2 benzoxazole is designated as B. 

---