Synthesis and photochromism of novel phenylene-linked photochromic bispyrans

reaction: see text] Phenylene-linked bisnaphthopyrans were synthesized in good yields via the one-pot reaction of bis-propargyl alcohols with naphthols. Temperature-dependent photochromism in 1,4-phenylene-linked bispyrans leads to up to 60 nm bathochromic shift between the colored species formed at room temperature and at -20 degrees C. Better fatigue resistance and higher colorability was observed in 1,4-phenylene-linked bis-2H]-naphtho1,2-b]pyrans by comparison to the 1,3-phenylene linked bis-2H]-naphtho1,2-b]pyrans.