Skeletal Rearrangement of Indole N‐Carboximidamides to 4‐(1H‐Indol‐3‐yl)‐N‐Aryl‐4H‐imidazo[4,5,1‐ij]Quinolin‐2‐amines
Year: 2025
Type: article
Abstract: Indole N‐carboximidamides (A) upon reaction with the base catalyst afforded a family of 4‐(1H‐indol‐3‐yl)‐N‐aryl‐4H‐imidazo[4,5,1‐ij]quinolin‐2‐amines (C) in yields up to 94% through unprecedented skeletal rearrangement involving NH deprotonation, C─Nindole 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. 1H 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 1H and 19F NMR spectroscopies.
Authors: Pragya Maheshwari, Natesan Thirupathi
Institution: University of Delhi
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: bronze
Funder: University of Delhi
Awards: G1333765613, G6093303865
OpenAlex ID: W4409271305