Photochromic Compounds

Abstract

Photochromic compds. of general structure I are prepd., where R = 3-furyl, 3-thienyl, 3-benzofuryl or 3-benzothienyl, R1 = alkyl or aryl, R2 = adamantylidene or R3R4C (R3, R4 = alkyl, aryl, heterocyclic group; or one of R3 and R4 is H and the other is alkyl or aryl), and X = O or NR5 (R5 = H, alkyl, aryl, aralkyl). I undergo reversible cyclization to bright red to deep purple forms when irradiated by UV light and are suitable for a wide range of recording and display devices. Thus, condensation of 3-acetyl-2,5-dimethylthiophene [2530-10-1] with di-Et isopropylidinesuccinate [42103-98-0] in C6H6 in the presence of NaH, acidification, hydrolysis of the liberated half ester, and cyclization by treatment with AcCl gave (Z)-[α-(2,5-dimethyl-3-thienyl)ethylidene]isopropylidenesuccinic anhydride [59000-90-7], which turned deep red when irradiated at 366 nm and then colorless when irradiated by white light. Thirteen other I were similarly prepd. Examples are also given which describe photochromic copying paper or screens prepd. by using I. [on SciFinder(R)]