Isoindolenine derivative

Isocyanate, Me, 431 phenyl, 431 Isocyanates, 58 acyl isocyanates, 92 alkyl isocyanates, 92, 118 aryl versus alkyl, 118 with hydrazinothiazoles, 100, 106 with 2-imino-4-thiazolines, 125 to mesoionic compounds, 65 to thiazolyl urea, 58, 92 Isoindolenine derivative, 56 Isomerism, E-Z equilibrium, 23 Isomerization, catalyst in aji-unsaturated acids, 438... 

Although phthalimidine (27, R = H) is formally at the isoindole oxidation level, its chemical properties are those of an amide. The corresponding cyclic imidate (28), which is formed from the amide using Meerwein s reagent in the normal way, is an isoindolenine derivative, however. Moreover, when the starting phthalimidine is 2-substituted, the product after basification is a 1-alkoxyisoindole (29).48,49... 

Tautomeric interconversions of 1,3-diimino-isoindolenine and its nitro and amino derivatives have been studied theoretically by the AMI method (97MI9). 

Although isoindole itself exists preferentially as such (73JCS(Pl)1432, 72TL4295, 77TL1095), in accord with predictions of MO calculations (77JA8248 and refs, therein), the low resonance energy of isoindoles often results in the isoindolenine tautomer being favored in substituted derivatives. 1H NMR spectroscopy has been especially useful in the study of this tautomeric... 

As expected, alkyl substitution also favors the isoindolenine, although accurate quantitative evaluation of proportions of tautomers is made difficult here by the instability of these derivatives.42 NMR measurements of 1,3,4,7-tetramethylisoindolenine indicate that this tautomer predominates over the corresponding isoindole by about 8 1.39... 

Various routes to 1,1,3-trisubstituted 1//-isoindoles have been reviewed.5 Thus, the triphenyl derivative 53 is available from the reaction of benzo-phenone imine with diphenyldichloromethane or by the Friedel-Crafts reactions between benzene and l,l,3-trichloro-lf/-isoindole. Recently, another route, which involves heating the cyclotriphosphatriazene 54 with benzophenone, has been described.86 The nitrone derivative 55 of the isoindolenine 53 may be obtained by treating the isoindolenine with m-chloroperbenzoic acid. This nitrone has also been obtained by the isomerization of the oxaziran 56 in the presence of a Lewis acid (Scheme 11).87... 

Electron-withdrawing substituents at C-l (C-3), conversely, favor the isoindole tautomer 74. For the 1-methoxycarbonyl and 1,3-dimethoxy-carbonyl derivatives, only the isoindole form is detected. The X-ray structure of l-formyl-3-phenylisoindole95 reveals the isoindole tautomer with a N—H bond length of 0.95 A. The NMR spectrum in d6-dimethyl sulfoxide shows a sharp signal at <59.96 (—CHO) and a broad signal at <513.74 (NH). The isoindolenine form is not detected.25... 

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