18591-57-6Relevant articles and documents
Discrimination in the solid-state photodimerization of 1-methyl-5,6- diphenylpyrazin-2-one
Kaftory, Menahem,Shteiman, Vitaly,Lavy, Tali,Scheffer, John R.,Yang, Jie,Enkelmann, Volker
, p. 847 - 853 (2005)
1-Methyl- and 1-ethyl-5,6-diphenylpyrazin-2-one crystallize in two modifications, one of which is light-stable and the other light-sensitive. The light-sensitive modification is known to undergo photodimerization in the solid state. This polymorph crystallizes in the monoclinic space group P21 with two crystallographically independent molecules in the asymmetric unit. The molecules are packed in stacks running parallel to the unique b axis. The two independent molecules are arranged alternately along the stack. In principle, there are two different pairs of molecules within a stack that can undergo photodimerization, and each should form a different enantiomer. A large crystal was irradiated and a solution of the product was separated by HPLC. The optical purity of the (+)-enantiomer sample was estimated to be greater than 90%. This finding indicates that only one of the two pairs undergoes photoreaction. The structure of a single crystal of the pyrazinone was elucidated by X-ray diffractometry before and after irradiation with a laser at a wavelength of 488 nm to 19% conversion. The results of the crystal-structure determinations provide additional evidence that only one of the two pairs of molecules undergoes photodimerization although there are no significant differences between the distances between the reacting centers. Furthermore, the latter results suggest that weak hydrogen bonds are a dominant factor that determines which of the two pairs is dimerized upon irradiation. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
C?H Methylation of Iminoamido Heterocycles with Sulfur Ylides**
Ghosh, Prithwish,Kwon, Na Yeon,Kim, Saegun,Han, Sangil,Lee, Suk Hun,An, Won,Mishra, Neeraj Kumar,Han, Soo Bong,Kim, In Su
supporting information, p. 191 - 196 (2020/10/29)
The direct methylation of N-heterocycles is an important transformation for the advancement of pharmaceuticals, agrochemicals, functional materials, and other chemical entities. Herein, the unprecedented C(sp2)-H methylation of iminoamido heterocycles as nucleoside base analogues is described. Notably, trimethylsulfoxonium salt was employed as a methylating agent under aqueous conditions. A wide substrate scope and excellent level of functional-group tolerance were attained. Moreover, this method can be readily applied to the site-selective methylation of azauracil nucleosides. The feasibility of gram-scale reactions and various transformations of the products highlight the synthetic potential of the developed method. Combined deuterium-labeling experiments aided the elucidation of a plausible reaction mechanism.
AN IMRPOVED PROCESS FOR THE PREPARATION OF SELEXIPAG OR ITS PHARMACEUTICALLY ACCEPTABLE SALTS
-
Page/Page column 11, (2017/08/01)
The present invention provides an improved process for Selexipag of formula (I) or its pharmaceutically acceptable salts.
