Potential Amino Groups

The amino form is usually much more favored in the equilibrium between amino and imino forms than is the hydroxy form in the corresponding keto-enol equilibrium. Grab and XJtzinger suggest that in the case of a-amino- and a-hydroxy-pyrroles, structure 89 increases the mesomeric stabilization and thus offsets the loss of pyrrole resonance energy, but the increase due to structure 90 is not sufficient to offset this loss. Similar reasoning may apply to furans and 

Pratesi, Atti accad. Lincei 16, 443 (1932) Chem. Abstr. 27, 2442 (1933). 

Sumpter and F. M. Miller, Heterocyclic Compounds with Indole and Carbazole Systems, pp. 53-54. Interscience, New York, 1954. 

The substituted 3-aminofurans (91, R = H, Me) resinify in air, can be diazotized (structure 91), and are easily hydrolyzed (structure 92 ).100 The infrared spectra of both 2- and 3-acetamidofuran show a strong NH stretching band indicating that these compounds do, indeed, exist in the acetamido form.101 

The a-aminobenzofuran 92a exists in the amino form shown, as evidenced by infrared10111 and proton resonance spectra.1011  

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VI. Compounds with a Potential Hydroxy and a Potential Amino Group. 132... 

It is now clear that the great majority of compounds containing potential amino groups exist in the amino form, although relatively little ciuantitative data are currently available and several discrepancies still await elucidation. As is always the case, the tendency for an amino compound to exist in the corresponding imino form is less than the tendency for a hydroxy compound to tautomerize to the 0X0 form. 

From a readily available racemic lower amino acid and a chiral auxiliary an heterocycle is built up, that is CH-acidic adjacent to the potential amino group and that contains two sites susceptible to hydrolysis. 

An efficient approach to the synthesis of a novel polyhydroxylated indolizidine derivatives containing an amino group has been developed. The key step of die synthesis involved microwave-assisted 1,3-dipolar cycloaddition of azasugar nitrone and methacrylate for installing a potential amino group and ester group with an extended chain (Li et al., 2009). 

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