A convenient method for the preparation of mono- and bis-substituted photochromic bis(benzothienyl)perfluorocyclopentenes via regioselective Friedel-Crafts acylation

The regioselective Friedel-Crafts acylation of 1,2-bis(2-methylbenzo[b]thien-3-yl)hexafluorocyclopentene was developed. Depending on the reaction conditions, mono- or bis(bromoacetyl) derivatives are formed as single products in good yields. Further heterocyclizations involving α-bromoketone moieties gave a series of new photochromic compounds.