Hydrogenation to the Amine

Hydrogenations of aromatic nitro compounds are important in industry. A nitro group can be easily introduced into a benzene ring and then hydrogenated to the amine. During the hydrogenation, a number of coupling and alkylation reactions are possible as depicted in Fig. 2.31. 

The imine group in the Schiff base PhMeC=NCH2Ph has been hydrogenated to the amine with 22% ee using the cationic DIOP complex in... 

PPhsP = CHR, with the aza-analogue PPhaP = NR (Scheme 5). The condensation of the aldehyde, generated in situ , with PPhsP = NR gives the imine, which was hydrogenated to the amine. 

G. S. Wayne, G. J. Snyder and D. W. Rogers, J. Am. Chem. Soc., 115, 9860 (1993). In this paper, the enthalpies of formation of the requisite azides were determined by hydrogenation to the amine and estimation of the latter enthalpies of formation. While far less is known about the enthalpies of formation of azides than amines, this approach seems without additional complication or significant error. 

Other 3-substituted morphinans were isolated during attempts to prepare 3-hydroxymorphinans by sequential nitration, hydrogenation to the amine, and diazotization of the unsubstituted precursor/381 A mixture of 2- and 3-nitromorphinans was isolated, but no biological data were reported. 

Ahyd was measured in w-hexane solution. Hydrogenation to the amine and nitrogen is thought to be clean and quantitative. Interference was observed, ascribable to adsorption of the amine product at the beginning, and catalyst poisoning at the end of the experiment. 

The chiral structural isomer sopromidine (265) was prepared from L-histidine (262) Scheme 5.59.). The amino acid was esteiified and reduced to the chiral alcohol (263) which was converted to the alkyl chloride and hydrogenated to the amine (264), enantiomerically pure (i )(-)-a-methylhis-tamine. Reaction with the isothiourea (256) then gave (265) [317-320]. 

The plant Crambe Abyssinica contains about 55% of erucic acid, and brassylic acid monomethyl ester is obtained from erucic acid methyl ester by ozonolysis. Treatment of the brassylic acid monoethyl ester with ammonium hydroxide/sulfuroxydichloride produces the nitrile, and this can be hydrogenated to the amine ... 

The presence of a salt such as CaGlg or NH4-acetate suppresses further hydrogenation to the amine.—E Diethylnitrosamine hydrogenated 2.25 hrs. with Pd-on-carbon in aq. 50%-alcohol in the presence of CaGl2 at 60° and 50 p.s.i.g. 

The precursor employed for the tracer experiment, [ 11- C]porphobilinogen, PBG (40), was prepared by reductive methylation of (41) with 60 % C-enriched formaldehyde to give (42), which was chlorinated to (43). The chloro-compound was converted into the azide (44) with sodium azide. The azide (44) was hydrogenated to the amine, which produced an intermediate lactam, then (40). 

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