Ea. Gonzalez et Mj. Lozano, NOVEL SYNTHESES OF BIS-SPIROPYRAN PHOTOCHROMIC COMPOUNDS USING ULTRASOUND II, Synthetic communications, 28(21), 1998, pp. 4035-4041
bis-Spiropyran photochromic compounds derivatives (3', 3'-trimethylind
oline-2-spiro-2'-benzopyran), were synthesized using ultrasonic energy
(25 kHz, 55 Watts). The reaction times were between 10 to 20 min. and
higher yields comparing; with the conventional reported methods, were
obtained.