Synthesis and Photochromic Characteristics of 1,3-Dihydrospiropyrimidobenzoxazines> and 1,3-Dihydrospirothiazolobenzoxazines>

Article abstract of DOI:10.1002/hlca.19920750419

Two new series of 1,3-dihydrospiro<2H-indole-oxazine> derivatives were synthesized, the 1,3-dihydrospiro<2H-indole-2,3'-<3H>pyrimido<5,4-f><1,4>benzoxazines> 4-10 and the 1,3-dihydrospiro<2H-indole-2,7'-<7H>thiazolo<5,4-f><1,4>benzoxazines> 11-17.These series extend the available range of photochromic properties (rate constant of thermal bleaching, UV/VIS spectrum of the opened coloured form, and photocoloration yield), an interesting feature of variable-transmission materials.The synthesis of these compounds (Scheme 1) required the preliminary synthesis of intermediate β-hydroxy-α-nitrosoheterocycles 18 and 19 (Scheme 2).Important amounts of a coloured, non-photochromic, stable secondary product (see 20) were formed in the condensation in the spiro series.The photochromic characteristics of the new derivatives were determined using a flash-photolysis apparatus coupled to a fast-scanning spectrometer.The role of the heteroatoms in the oxazine moiety and the role of substituents in the indole moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects.The presence of an S-atom gives rise to interesting properties which open up new prospects for synthesis and applications.