Photochemical transformations of small ring heterocyclic systems. LX. Photochemical ring-opening reactions of substituted chromenes and isochromenes

Abstract

the three stereoisomers. The results of this experiment are recorded in Table IV.Photostationary State Compositions from Irradiations of ltt with Various Triplet Sensitizers. Spectrograde cyclohexane solutions of trans,trarcs-bis(/3-styryl)dimethylsilane (1.0 X 10-2 M) and the various triplet sensitizers (acetone, benzophenone, 1-acetonaphthone, and benzil), each 2.0 X ID-2 M, were placed individually in Pyrex test tubes and irradiated with Pyrex-filtered light until the photostationary states were obtained. Analyses of these solutions by gas chromatography yielded photostationary state isomer compositions tabulated in Table V.Acknowledgment. Support of these studies by the Robert A. Welch Foundation is gratefully acknowledged. P.S.M. would like to thank the Environmental Quality Program at Texas A&M University for funds to purchase gas chromatographic equipment used in these studies.

Synthesis and Photochromic Behaviour of Naphthopyrans, Pyranoquinolines, Pyranoquinazolines and Pyranoquinoxalines

“…An improvement of the photochromic properties was obtained mainly by using benzo-annulated chromenes, namely the naphthopyrans. Moreover, ' several studies have undoubtedly shown that the alkyl groups at the sp3-C-atoms should be replaced by a spiroadamantane moiety [12] [13], a cyclopropyl group [14] [15], or two aryl substituents to manifest photochromic behaviour at room temperature [16] [17] and to prevent rapid fatigue under photoexcitation [18]. During our study in the field of photoresponsive systems, we reasoned that 2,2-diaryl-2H-chromenes would be a good parent system for such species.…”

Furo-fused 2H-chromenes: synthesis and photochromic properties

“…Indeed, the first described chromenes, 2,2-dimethyl-[2H]-chromenes and their 2H-1Benzo~~rans (or 2H-chr0menes) are an benzoannulated derivatives (naphthopyrans), showed photoparticularly attractive because chromic behavior only at low temperature (2) and, moreover, of their P~~~~~~~~~~~ properties. Indeed, 2H-chromenes led to undesirable by-products (4). In fact, interest in research a ring of the pyran (2).…”

Synthesis and photochromic behaviour of new methyl induced linear and angular thieno-2H-chromenes

“…Comparing the spectra of the open forms of the angular compounds 5a and 5b (annellation 5,6) with compound 7 it is possible to conclude that the methyl group of the benzene ring increases the bathochromic effect for λ 2 of 10 nm and the colourability in both wavelengths is slightly increased. A comparison could also be done between compound 5a and the corresponding benzothieno-2H-chromene 8 prepared and studied by some of us 16 (Fig 2), having the same type of annellation (5,6) and the same regio-isomery (S- The presence of the methoxy groups in the benzene rings of the sp 3 carbon of compound 5b had a bathochromic effect in both wavelengths and the colourability increases significatively in both cases comparing to 5a (Table 1). (Fig 1.).…”

“…In order to gain reasonable stability of the coloured forms and to prevent rapid fatigue under photoexcitation, it is required to introduce bulky substituents into the 2-position of the pyran ring especially phenyl groups. 5,6 Several five membered 5,6 heteroannellated 2H-chromenes have been prepared and the effect of the heteroannellation on their photochromism was determined. 7 Angular 2H-chromenes heteroannellated at 5,6 and 7,8 positions with a 2,3-dimethylthiophene ring were prepared by us earlier and their photochromic behaviour was studied.…”