Experimental and theoretical investigation of the coarctate cyclization of (2-Ethynylphenyl)phenyldiazenes.
A new route to substituted 2-phenyl-2H-indazoles through the cyclization of (2-ethynylphenyl)phenyldiazenes is presented. A coarctate reaction pathway forms the isoindazole carbene under neutral conditions, at moderate temperatures, and without the requirement of a carbene stabilizer. A wide variety of previously unknown diazene precursors was synthesized and cyclized. Trapping of the carbene with a silyl alcohol followed by deprotection affords the 3-hydroxymethyl-2-phenyl-2H-indazoles in good overall yield. The free carbene could also be trapped as a [2 + 1] cycloadduct with 2,3-dimethyl-2-butene.
Department of Chemistry, University of Oregon, Eugene, Oregon 97403-1253, USA.
Laura D
LD
Shirtcliff
Timothy J R
TJ
Weakley
Michael M
MM
Haley
Felix
F
Köhler
Rainer
R
Herges