Cu-catalyzed selective cascade sp³ C–H bond oxidative functionalization towards isoxazoline derivatives

Abstract

The first Cu-catalyzed cascade sp(3) C-H bond oxidative functionalization of the 2-ethylazaarenes has been developed. The two different sp(3) C-H bonds in 2-ethylazaarenes are selectively oxidized and four new types of bonds (C=O, C=N, C-C, C-O) are constructed in one operation. Starting from the simple substrates and cheap nitro source, this reaction provides an efficient approach to produce new kinds of isoxazolines.

Ir4(CO)12-Catalyzed Benzylic C(sp3)–H Silylation of 2-Alkylpyridines with Hydrosilanes Leading to 2-(1-Silylalkyl)pyridines

“…The synthesis of 3-azaaryl-substituted isoxazoline derivatives was achieved via the Cu-catalyzed direct C–H nitration of 2-alkylazaarenes to generate the corresponding nitrile oxides, followed by 1,3-dipolar cycloaddition with alkenes or alkynes . The α-oxidation of 2-alkylquinolines catalyzed by Cu salts was demonstrated, by which the products underwent further transformations in situ . Li, Wang, and coauthors reported the unique tautomerization of 2,6-lutidine·B­(C 6 F 5 ) 3 adducts in the presence of a catalytic amount of catecholborane to form zwitter ionic [(6-methylpyridinium-2-yl)­methyl]­borates .…”

Cu-catalyzed sp3 C–H bond oxidative functionalization of alkylazaarenes and substituted ethanones: an efficient approach to isoxazoline derivatives

“…When 2-ethylquinoline was used as substrate under the standard condition, a cascade sp 3 C-H bond oxidative functionalization was achieved to access the different isoxazoline derivatives. [9] Table 2. Substrates scope: acetophenone.…”

Peroxydisulfate as an Oxidant in the Site‐Selective Functionalization of sp3 C–H Bonds

“…These reactions failed to proceed with other heterocycles such as quinolines and thiazoles. Yang and co‐workers have developed a synthesis for isoxazole and isoxazaline derivatives of alkyl aza‐arenes and aryl ketones involving a tandem reaction sequence of sp 3 C–H nitration, oxidation to a nitrile oxide, and 1,3‐dipolar cycloaddition with an alkyne or alkene (Scheme ) ,…”