Synthesis of Hydroxylated Polycyclic Pyrrolo/Indolo[1,2-a]quinoxaline-Fused Lactam Derivatives via PhI(OAc)₂-Promoted 1,2-Bond Migration and Solvent Insertion

Abstract

PhI(OAc) 2 -mediated ring expansion via 1,2-bond migration and concurrent solvent insertion generate hydroxylated polycyclic pyrrolo/indolo[1,2-a]quinoxaline-fused lactam derivatives in a highly diastereoselective fashion from spiro-fused quinoxalines in good-to-excellent yield. X-ray crystal structure analysis reveals that the polycyclic lactams are nonplanar molecules devoid of any symmetry as they possess one or two axially chiral biaryl or N-arylindolyl bridges along with one chiral center at the bridgehead carbon.

AlCl3-Promoted Intramolecular Indolinone-Quinolone Rearrangement of Spiro[indoline-3,2′-quinoxaline]-2,3′-diones: Easy Access to Quinolino[3,4-b]quinoxalin-6-ones

“…Based on the results obtained (Table ) and previous literature data, the DFT-computed reaction free energy profile (at 200 °C and 1 M concentration) at the PW6B95-D3/def2-TZVP + COSMO-RS // TPSS-D3/def2-SVP + COSMO level in acetic acid solution is depicted in Scheme . Initially, the dimeric Lewis acid(AlCl 3 ) 2 gets coordinated to the lone pair of C3′ carbonyl oxygen of spiro­[indoline-3,2′-quinoxaline]-2,3′-diones 5g , which is thereby activated, to form the donor–acceptor complex A in a −14.1 kcal/mol exergonic step.…”

Applications of phenyliodine(III) diacetate in heterocyclic ringformations: An updatefrom 2015 to date

“…Mandal and Pramanik have very recently reported that indolo[1,2‐a]quinoxaline‐fused lactam derivatives were produced by hydroxylating polycyclic pyrrolo/indolo[1,2‐a]quinoxaline and PIDA‐mediated ring expansion via 1,2‐bond migration and the yields ranged from good to excellent and with excellent diastereoselectivity from spiro‐fused quinoxalines (Scheme 33) [54].…”

“…The cyclization of III through imine creation is the last step, and it produces the required vanillyl benzodiazepines with good yields. good to excellent and with excellent diastereoselectivity from spiro-fused quinoxalines (Scheme 33) [54].…”

An Alkyne–Isocyanide Cycloaddition/Boulton-Katritzky Rearrangement/Ring Expansion Reaction: Access to 9-Deazaguanines

“…This pyrrole structure with two electron-withdrawing groups is deprotonated under basic conditions and then participates in a Boulton-Katritzky rearrangement (BKR), leading to the formation of a spiro 3 H -pyrrole intermediate ( II ), which then undergoes rapid ring expansion via acyl migration to afford the fused 9-deazaguanine product ( 4aa ) (Scheme a, path B). Such ring-expansion strategies from unstable spirocyclic intermediates have also been exploited in a variety of excellent examples by Toste, Shi, You, Kim and Oh, Babu, and others and provide important solutions for the formation of fused heterocycles with challenging structures.…”