A new family of hypervalent iodine
reagents containing transferable
primary amine groups is described. Benziodoxolone-based reagents were
synthesized on the gram-scale through operationally simple reactions
in up to quantitative yields. These bench-stable solids were characterized
by X-ray analysis and successfully employed in the α-amination
of indanone-based β-ketoesters in up to 83% yield. Mechanistic
studies indicate a substitution mechanism involving an electrophilic
amine.
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In the past few years, the number of protocols for α-amination of carbonyl compounds has dramatically increased, highlighting the importance of this moiety. While some classical approaches continue to be used, supported by novel catalysts, new methods with unique advantages have also emerged. Among these, a wide variety of conditions can be observed such as the use of umpoled enolates with nucleophilic nitrogen sources; the generation of electrophilic nitrogen sources; and oxidative methods, generally through the generation of radical species. This review aims to compile the most recent publications for the α-amination of carbonyls on the basis of synthetic utility, novel transformations and enantioselectivity.
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