Hydrogenation of imides

Fig. 12 Chemoselective hydrogenation of imides with bifunctional Cp Ru(P-N) catalyst...

C, A-diphenyl nitrones (p-XC6H4CHN(0)Ph, X = NO2, Cl, H, Me and MeO) with N-phenylmaleimide to form 2,3,6-triaryl derivatives of l-oxa-2,6-diazabicyclo[3.3.0]octane-5,7-dione. No enthalpy of formation data are available for A-phenylmaleimide or for maleimide itself. However, it is available for the corresponding A-methyhnaleimide along with some other imides. The gas phase enthalpy of hydrogenation of this species (derived as the difference between its enthalpy of formation and that of N-methylsucc-inimide ) is 133.7 2.2 kJmoC. This value is essentially the same as for ethylene (derived as the difference between its enthalpy of formation and that of ethane) of 136.3 0.4 kJmoH. Therefore, let us assume the reaction of the above parent nitrone with ethylene to form the diphenylated isoxazolidine, shown in equation 12, has very much the same exothermicity as with A-phenylmaleimide, namely ca 82 kJmol . If so, the enthalpy of formation of 2,3-diphenylisoxazolidine would be 233 kJmol . Now, is this value plausible ... 

The 2-alkyl and 2-aryl derivatives are best prepared by the reaction between 1,3,5-triazine and an imidate or amidine (see Section 2.20.3.1.2). 2-Amino-l,3,5-triazines may be prepared efficiently by (a) treatment of 1,3,5-triazine with 1-amidinopyrazole (see Section 2.20.3.1) (b) condensation of triformidomethane and a formylguanidine (see Section 2.20.4.3.3). 2-Aryloxy derivatives are produced by hydrogenation of the corresponding dichloro-l,3,5-triazine derivative (see Section 2.20.3.12). 

Asymmetric hydrogenation of camphor-derived sultamimides (l).2 Hydrogenation of these imides catalyzed by Pd/C proceeds with >90%... 

The H atoms were also located and are included in the refinement. The centrosymmetric dimer (CgH CO NHSO g mols. are formed by hydrogen bonds between the N of imide and 0 of the carbonyl atoms, (NH.0C), of the five membered ring system of saccharin. The six-sided ring formed by the hydrogen bonds around the center of symmetry is completely planar. The location of the H atom eliminates the possibility of the lactim structure for... 

As discussed in Sec. 3.3.1.4, besides ketones also imides can be used as reactants in the Norrish-Yang reaction. For clarity, photochemical reactions of imides, which are initiated by a hydrogen abstraction both... 

The Gabriel method of making primary amines (Scheme 2.33) rests on the fact that the imide hydrogen of phthalimide is rendered acidic by the two carbonyl groups. It therefore forms a potassium salt, which is a powerful nucleophile and may be alkylated. Hydrolysis of the amide generates the primary amine. The cleavage of the phthalimide may be carried out with hydrazine (H NNHj). 

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