Synthesis of Dihydrophenanthridines and Oxoimidazolidines from Anilines and Ethylglyoxylate via Aza Diels–Alder Reaction of Arynes and KF-Induced Annulation

Abstract

The transition-metal-free multicomponent coupling of arynes, anilines, and ethylglyoxylate, proceeding via an inverse electron-demand aza Diels-Alder cycloaddition and N-arylation, has been demonstrated. This protocol allows rapid access to N-aryl dihydrophenanthridine derivatives in moderate to high yields at room temperature from readily available starting materials. In addition, an unprecedented fluoride induced annulation of ethyl(arylimino)acetates led to the formation of highly functionalized oxoimidazolidine derivatives in good yields under mild conditions.

Reactions of HDDA Benzynes with C,N‐Diarylimines (ArCH=NAr')

“…These reactions proceed considerably more efficiently than those reported earlier for imine trapping of benzyne itself (from benzenediazonium‐2‐carboxylate thermolysis). In no case have we observed products arising from initial [4+2] cycloaddition, as has been seen in previous studies , , , , . This work represents another instance in which the arynes generated through the HDDA‐cycloisomerization reaction, which are produced in a purely thermal environment, has allowed for the formation of the trapping products in a much cleaner, if not unique, manner.…”

“…In 2006 Wang et al showed that benzyne could be used in a 3‐component process to access phenanthridines 7c with high efficiency using an electron‐poor benzaldehyde and an electron‐rich aniline. Similarly, in 2016 researchers in the He group were able to isolate 7b in a three‐component process using Kobayashi arynes, an aldehyde ester, and an aniline. In 2015 Coquerel and co‐workers reported the formation of isoquinolines 7d derived from an imine containing a nitrogen‐bound pyrazole moiety, and, through a computational study, suggested that an electron‐rich aromatic group bound to the imine nitrogen favors [4+2] cycloaddition over a [2+2] pathway.…”

Synthesis of Tetrahydro-1H-indeno[1,2-b]pyridine via Cascade Cyclization and Friedel–Crafts Reaction

“…The formation of 9s , t is shown in Scheme . In this case, aldehyde 5 enolized under Lewis acidic conditions, which subsequently reacted with alkyne 4 to form the Diels–Alder adduct 13 , which after aromatization gave naphthalene derivatives 9s , t …”

Synthesis of functional 2-substituted 1,3-dinitroimidazolidines. A new synthetic approach to high-energy compounds

“…However, there are few data on the synthesis of analogous structures. [25][26][27][28] Acid 1 was synthesized by three methods. In the first method (Method A), glyoxylic acid ethyl ester (2) was condensed with potassium ethylene-1,2-disulfamate (3) at pH=3.4 and 45-50°С to furnish potassium 2-(ethoxycarbonyl)imidazolidine-1,3-5 disulfonate (4), which was then nitrated with concentrated HNO3 at between -35°С…”