1,3-Dipolar cycloaddition reactions of phthalic anhydrides with an azomethine ylide

Abstract

A series of phthalic anhydrides underwent a 1,3-dipolar cycloaddition reaction with N-benzylazomethine ylide to produce unstable spiro(isobenzofuran-1,5′-oxazolidin)-3-ones, which underwent a subsequent reductive ring-opening reaction to afford 1(3H)-isobenzofuranones.

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

“…Additionally, ~100 (48:52) and electronic effects of the methoxy group on the adjacent carboxyl group having the effect of raising the transition state energy and lowering the rate of reactivity of the adjacent carboxyl group. The reductive ring-opening of the spiro-oxazolidines 200 was also investigated [41]. Treatment of the oxazolidines with NaBH4 in methanol led to conversion, in reasonable yields, to 3-hydroxyisobenzofuran-1-ones 201 (Table 28).…”

“…Cycloaddition of azomethine ylide 172, formed from silylamine reagent 178, with isatoic anhydrides 5a, followed by conversion of the oxazolidines 195 to 1,3-benzodiazepin-5-ones 196. In a recent development, phthalic anhydrides 5b were reported to undergo cycloaddition with the azomethine ylide 172, formed from reagent 178 under conditions of trifluoroacetic acid catalysis [41]. The generated spiro-oxazolidine cycloadducts 200 proved to be more stable than the analogous cycloadducts generated from isatoic anhydrides 5a.…”

“…The reductive ring-opening of the spiro-oxazolidines 200 was also investigated [41]. Treatment of the oxazolidines with NaBH 4 in methanol led to conversion, in reasonable yields, to 3-hydroxy-isobenzofuran-1-ones 201 (Table 28).…”

Current Trends towards the Synthesis of Bioactive Heterocycles and Natural Products Using 1,3-Dipolar Cycloadditions (1,3-DC) with Azomethine Ylides

“…The reaction of an azomethine ylide with the carbonyl group of an anhydride is not common, however, the dipole generated in situ from N-silylated benzylamine 221 reacted with phthalic anhydrides 220 affording spirooxazolidines 222 in very good yields and elevated regiocontrol (Scheme 64). 95…”

Merging Imidazolidines with a Trifluoromethylated Tetrasubstituted Carbon through Tungsten Catalyzed 1,3-Dipolar Cycloaddition

“…The 1,3-dipole cycloaddition between N -benzyl azomethine ylide and an unsaturated bond, such as an alkene, an alkyne, an anhydride, a cyano, an aldehyde, a ketone, an imine, and an aromatic CC bond, has become a promising strategy for the construction of N -containing heterocycles. However, owing to the normal challenging issues associated with the construction of a fully substituted carbon and the steric hindrance and electrostatic repulsions arising from the effect of the CF 3 group, the 1,3-dipole cycloaddition between acyclic trifluoromethylated ketimines and certain 1,3-dipoles remains unaddressed, although the CF 3 group has a strong electronic effect on the electrophilic character of dipolarophiles, which would deliver N -heterocycles bearing a CF 3 -tetrasubstituted carbon.…”