Ru(ii)-catalyzed regioselective [4 + 1] redox-neutral spirocyclization of aryl amidines with diazopyrazolones: direct access to spiro[indole-3,4′-pyrazol]-5′-ones

Abstract

An efficient protocol to construct spiro[indole-3,4'-pyrazol]-5'-ones via ruthenium(II)-catalyzed selective C-H bond activation/[4 + 1] spirocyclization starting from easily available N-aryl amidines and diazopyrazolones has been developed. A series of spiro-pyrazolones...

Recent approaches for the synthesis of heterocycles from amidines via a metal catalyzed C–H functionalization reaction

“…Cui, Lin and co-workers developed a Ru( ii )-catalyzed chemoselective and regioselective C–H acyivation/spirocyclization reaction to synthesize complex spirocycles products with distinctive structures. 36 The KIE results showed that the cleavage of the C–H bond might be the rate-determining step. Meanwhile, it is more straightforward to activate the C–H bond by connecting the electron-donating substituent in the aromatic ring (Scheme 23).…”