Skeletal Rearrangement of Indole <i>N</i>‐Carboximidamides to 4‐(1<i>H‐</i>Indol‐3‐yl)‐<i>N</i>‐Aryl‐4<i>H‐</i>imidazo[4,5,1‐<i>ij</i>]Quinolin‐2‐amines

Abstract Indole N ‐carboximidamides ( A ) upon reaction with the base catalyst afforded a family of 4‐(1 H‐ indol‐3‐yl)‐ N ‐aryl‐4 H‐ imidazo[4,5,1‐ ij ]quinolin‐2‐amines ( C ) in yields up to 94% through unprecedented skeletal rearrangement involving NH deprotonation, C─N indole bond cleavage, C─N and C─C bond formations, all in one flask. The scope of the substrates was studied and diverse sets of functional groups were tolerated (25 examples). The electron poor ( 26 ), sterically hindered and base sensitive ( 30 and 43 ) and electron donating ( 48 ) substrates gave either poor yield or no products of the type C . A competition experiment involving a pair of electronically distinct A was carried out. Two carbodiimide intermediates 81 and 88 were trapped with 2‐phenylindole, pyrrole, and water nucleophiles to afford 3‐dimensional products 82 , 85 , and 89 and a modified intermediate 93 to strengthen the mechanism of the A → C rearrangement. A gram‐scale synthesis of 7 is reported in 90% yield. 1 H NMR monitoring experiment was carried out at 343 K for the 6 → 7 rearrangements to better understand the mechanism. The number and nature of solution species of C were studied by VT 1 H and 19 F NMR spectroscopies.