Synthesis and photochromic behaviour of new methyl induced linear and angular t...

• Author(s): Queiroz, Maria João R. P. ; Plasencia, Paula M. S. ; Dubest, Roger ; Aubard, Jean ; Guglielmetti, Robert J.
• Date: 2003
• Persistent ID: http://hdl.handle.net/1822/2200
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Thieno-2H-chromenes; Hydroxybenzo[b]thiophenes; Photochromism; Flash photolysis
• Document Type: Article
• Language: English

Description

New methyl induced linear and angular thieno-2H-chromenes 4, 5 and 6 were prepared by reaction of new methylated 6-hydroxybenzo[b]thiophenes 2 (a, b and c) and propargylic alcohols 3a and 3b, using acidic Alumina Brockmann I as catalyst and drying agent. Compounds 2 were prepared in good to excellent yields in a “one pot” three step reaction from the corresponding bromo compounds 1. The photochromic behaviour of compounds 4, 5 and 6b was evaluated with the aid of a classical set of spectrokinetic parameters, and compared to reference compounds that are benzoannellated in the 5,6 and 6,7 positions of the chromene (naphthopyrans) and also to thieno-2H-chromenes 7 and 8, previously prepared, which are analogues of 5a. The resistance to fatigue (photodegradation) under continuous irradiation was also evaluated.