1025-85-0Relevant articles and documents
Chapter Open for the Excited-State Intramolecular Thiol Proton Transfer in the Room-Temperature Solution
Chang, Chao-Che,Chen, Chao-Tsen,Chou, Pi-Tai,Huang, Chun-Hao,Li, Elise Y.,Liao, Yu-Chan,Liu, Yi-Hung,Liu, Zong-Ying,Meng, Fan-Yi,Wang, Chun-Hsiang
supporting information, p. 12715 - 12724 (2021/08/30)
We report here, for the first time, the experimental observation on the excited-state intramolecular proton transfer (ESIPT) reaction of the thiol proton in room-temperature solution. This phenomenon is demonstrated by a derivative of 3-thiolflavone (3TF), namely, 2-(4-(diethylamino)phenyl)-3-mercapto-4H-chromen-4-one (3NTF), which possesses an - S - H···O= intramolecular H-bond (denoted by the dashed line) and has an S1 absorption at 383 nm. Upon photoexcitation, 3NTF exhibits a distinctly red emission maximized at 710 nm in cyclohexane with an anomalously large Stokes shift of 12 230 cm-1. Upon methylation on the thiol group, 3MeNTF, lacking the thiol proton, exhibits a normal Stokes-shifted emission at 472 nm. These, in combination with the computational approaches, lead to the conclusion of thiol-type ESIPT unambiguously. Further time-resolved study renders an unresolvable (180 fs) ESIPT rate for 3NTF, followed by a tautomer emission lifetime of 120 ps. In sharp contrast to 3NTF, both 3TF and 3-mercapto-2-(4-(trifluoromethyl)phenyl)-4H-chromen-4-one (3FTF) are non-emissive. Detailed computational approaches indicate that all studied thiols undergo thermally favorable ESIPT. However, once forming the proton-transferred tautomer, the lone-pair electrons on the sulfur atom brings non-negligible nπ? contribution to the S1′ state (prime indicates the proton-transferred tautomer), for which the relaxation is dominated by the non-radiative deactivation. For 3NTF, the extension of π-electron delocalization by the diethylamino electron-donating group endows the S1′ state primarily in the ππ? configuration, exhibiting the prominent tautomer emission. The results open a new chapter in the field of ESIPT, covering the non-canonical sulfur intramolecular H-bond and its associated ESIPT at ambient temperature.
Utilization of "2-Pyrrolidone Hydrotribromide" in the Synthesis of Flavones
Takeno, Noboru,Fukushima, Tohoru,Takeda, Shin-ichi,Kishimoto, Kazuyasu
, p. 1599 - 1600 (2007/10/02)
The reaction of flavanone with "2-pyrrolidone hydrotribromide" in tetrahydrofuran gave 3-bromoflavanone in a good yield.On the other hand, flavone was obtained in 97percent yield when this reaction was carried out in dimethyl sulfoxide at 80 deg C.Under the same conditions, most flavones were obtained from the corresponding flavanones in high purity and good yiels.
Pyrolitic Elimination of Hydrogen Halide and Halogen from 2,3-Dihalogenoketones
Donnely, John A.,Quigley, Killian
, p. 1299 - 1305 (2007/10/02)
The thermal elimination of hydrogen chloride from 2'-hydroxychalcone dichlorides occured in two stages, initially forming 3-chloroflavones and then flavones; α-chloro-2'-hydroxychalcones, the likely intermediates in the formation of 3-chloroflavones, also yielded the same products.The pyrolysis of 2'-hydroxychalcone dibromides resulted in debromination as well as dehydrobromination with the consequent appearence of brominated flavones among the products.The formation of 3-bromoflavones was not observed but the isomeric (E)-α-bromo-2'-hydroxychalcones thermally isomerized to their (Z)-isomers and then underwent cyclization and dehydrobromination.The bromide were considerably more reactive than the dichlorides but, as a synthetic procedure, the pyrolysis of the dichlorides is cleaner and more productive.
