Acid-Catalyzed Cyclization Reactions of Substituted Acetylenic Ketones: A new Approach for the Synthesis of 3-Halofurans, Flavones, and Styrylchromones
作者:Daniel Obrecht
DOI:10.1002/hlca.19890720305
日期:1989.5.3
Acetylenic acetals of type I(Scheme 1) and acetylenic ketones of type III(Scheme 1), 37 and 38(Scheme 7) are versatile synthetic precursors for the synthesis of various heterocycles by acid-catalyzed cyclization reactions. By this way, substituted 3-halofurans of type II and IV(Scheme 1) and flavones and styrylchromones (Scheme 7) can be synthesized in good-to-excellent yields. The high degree of regioselectivity
Photochromic and fluorescent properties of bisfurylethene derivatives
作者:Tadatsugu Yamaguchi、Masahiro Irie
DOI:10.1039/b611294c
日期:——
Photochromic diarylethenes having furan units (1 and 3) were synthesized and their photochromic performances were compared with those having thiophene units. The cyclization quantum yields of both derivatives in hexane are similar. In contrast, the cycloreversion quantum yield of the derivative having furan units (1) is much larger than that having thiophene units (2) in hexane. The difference is attributed to the conformation of the closed-ring isomers. Although 2a and 4a do not show any fluorescence, 1a and 3a exhibit fluorescence. Photochromism in the single crystalline phase was also observed for 1 and 3. Upon irradiation with 313 nm light, the colorless crystals 1 and 3 changed to violet and yellow, respectively.