An in-depth study of the azidobenzophenone–anthranil–acridone transformation

Abstract

The title transformation, particularly the conversion of anthranils into acridones, is shown to be critically sensitive to temperature, solvent, substituent, and metal catalysts. Thus the conversion of 3-(p-tolyl) anthranil into an acridone gives a ratio of 2and 3-methyl derivatives varying from 0.6 : 1 to 4.7 : 1 with changing temperature and solvent. In other similar thermolyses, solvents (e.g. 1,2,4-trichlorobenzene) were incorporated into the product and traces of metals and their derivatives had a dramatic effect on the rate and course of the reaction. The most effective catalysts were iron powder and aluminium acetylacetonate. 3-(2,6-Disubstituted pheny1)anthranils gave acridones in which the substituents were either lost or rearranged onto N or C, the last cases involving sequential [I ,5] -sigmatropic shifts.3-Thienylanthranils gave related thienoquinolones on thermolysis ; again the reactions were very sensitive to catalysis. Blocked thienylanthranils also gave rearrangement products, but the non-aromatic intermediates could be isolated.5 "C and mixed m.p.s are only slightly depressed thus accounting for Bamberger's erroneous interpretation,

RuCl2(dmso)4 Catalyzes the Solvent‐Free Indirect Friedländer Synthesis of Polysubstituted Quinolines from Alcohols

“…[26] Ketone 1c [27] was prepared in 81 % overall yield by treatment of isatoic anhydride with N,O-dimethylhydroxylamine hydrochloride in aqueous ethanol to give the corresponding 2-aminobenzamide, which then was treated with 4-methoxyphenyllithium obtained in situ from butyllithium and 4-bromoanisole by literature procedures. [28] Alcohol 5 [29] was prepared in 87 % yield by standard reduction of the ketone 1b with NaBH 4 in ethanol.…”

Transition Metal‐Catalyzed Formation of N‐Heterocycles via Aryl‐ or Vinyl C–H Bond Amination

“…Meth-Cohn and co-workers reported 3-aryl-substituted anthranil 8 could be converted to an acridone 9 and 10 by exposure to a variety of different transition metal salts (Scheme 2). [6] In addition to acridones 9 and 10, aniline 11 was observed. The observation of aniline led the authors to implicate a metal nitrene as a reactive intermediate, which was formed upon cleavage of the N-O bond in anthranil 8.…”

“…On the basis of these experiments, Gaunt and co-workers propose that the aryl C-H bond amination occurs through the reaction of polynuclear palladium species. Recently, Gaunt and co-workers reported that 2,3-disubstituted N-arylindolines 111 could be accessed if the diacetoxyiodobenzene oxidant was substituted with copper acetate [Equation (6)]. [52] Critical to the success of this transfor-…”

General synthesis of 2,1-benzisoxazoles (anthranils) from nitroarenes and benzylic C–H acids in aprotic media promoted by combination of strong bases and silylating agents

“…2,1-Benzisoxazoles (anthranils) are important compounds, particularly as starting materials for the synthesis of 2-aminoarylketones [ 1 – 4 ]. A number of heterocyclic systems, such as quinolines, acridines, or quinazolines, can be synthesized either from the latter or, in some cases, directly from 1,2-benzisoxazoles [ 1 – 10 ] (Scheme 1 ).…”