- Molybdenum-silver co-catalyzed cycloaddition of alkynes with: N -isocyanoiminotriphenylphosphorane (NIITP): An efficient strategy for the synthesis of monosubstituted pyrazoles
-
A new molybdenum-silver co-catalyzed [3+2] cycloaddition of alkynes with N-isocyanoiminotriphenylphosphorane (NIITP) has been described. The NIITP serves as a non-toxic, facile "CNN" source. Over 30 substrates were successfully converted to the desired compounds in good to excellent yields.
- Mi, Pengbing,Lang, Jiajia,Lin, Shaojian
-
supporting information
p. 7986 - 7989
(2019/07/10)
-
- Silver-Mediated [3 + 2] Cycloaddition of Alkynes and N-Isocyanoiminotriphenylphosphorane: Access to Monosubstituted Pyrazoles
-
A silver-mediated [3 + 2] cycloaddition of "CNN" and "C≡C" for constructing pyrazoles has been described. The "CNN" building block used is N-isocyanoiminotriphenylphosphorane, which is a stable, safe, easy-to-handle, and odorless solid isocyanide. The reaction is characterized by its mild conditions, broad substrate scope, and excellent functional group tolerance.
- Yi, Fanhua,Zhao, Wanjun,Wang, Zikun,Bi, Xihe
-
supporting information
p. 3158 - 3161
(2019/05/10)
-
- New ultraviolet stabilizers: 3- and 5-(2′-hydroxyphenyl)pyrazoles
-
A new class of ultraviolet stabilizers, the C-(2?-hydroxyphenyl)pyrazoles, is described. The combined use of X-ray crystallography [3(5)-(2′-hydroxyphenyl)pyrazole (5), l-methyl-3-(2′-hydroxyphenyl)pyrazole (7), and 1-methyl-5-(2?-hydroxyphenyl)pyrazole (8)], NMR (1 and 13C), and UV spectroscopies allows the determination of the major tautomers, the coplanarity of both rings if present, and the existence of hydrogen bonds. Compounds 5 and 7, in which there is an intramolecular hydrogen bond (IMHB), do not fluoresce in cyclohexane. Solvent and temperature experiments prove that for these compounds in cyclohexane proton transfer took place in the excited singlet state but not in the triplet state (phosphorescence) and that the latter one is of higher energy than the former. The fact that the absorptions of planar 1-methyl-3-(2′-methoxyphenyl)pyrazole (9) and nonplanar 1-methyl-5-(2′-methoxyphenyl)pyrazole (10) are quite different whereas their emissions are very similar suggests that 10 might behave as a laser dye in the UV region (from an excited planar form to a ground state nonplanar form). Finally, the photostability of (2'-hydroxyphenyl)- and (2′-methoxyphenyl)pyrazoles was determined, compound 7 being even more stable than Tinuvin P.
- Catalán, Javier,Fabero, Fernando,Claramunt, Rosa M.,Dolores Santa Maria,De la Concepción Foces-Foces,Cano, Felix Hernández,Martínez-Ripoll, Martín,Elguero, José,Sastre, Roberto
-
p. 5039 - 5048
(2007/10/02)
-