We report here a reaction that selectively
deaminates primary amines
and anilines under mild conditions and with remarkable functional
group tolerance including a range of pharmaceutical compounds, amino
acids, amino sugars, and natural products. An anomeric amide reagent
is uniquely capable of facilitating the reaction through the intermediacy
of an unprecedented monosubstituted isodiazene intermediate. In addition
to dramatically simplifying deamination compared to existing protocols,
our approach enables strategic applications of iminium and amine-directed
chemistries as traceless methods. Mechanistic and computational studies
support the intermedicacy of a primary isodiazene which exhibits an
unexpected divergence from previously studied secondary isodiazenes,
leading to cage-escaping, free radical species that engage in a chain,
hydrogen-atom transfer process involving aliphatic and diazenyl radical
intermediates.
This review covers recent and historical aliphatic deaminative functionalization reactions to encourage the use of primary amines as aliphatic building blocks.
Selective functional group interconversions in complex molecular settings underpin many of the challenges facing modern organic synthesis. Currently, a privileged subset of functional groups dominates this landscape, while others, despite their abundance, are sorely underdeveloped. Amines epitomize this dichotomy; they are abundant but otherwise intransigent toward direct interconversion. Here, we report an approach that enables the direct conversion of amines to bromides, chlorides, iodides, phosphates, thioethers, and alcohols, the heart of which is a deaminative carbon-centered radical formation process using an anomeric amide reagent. Experimental and computational mechanistic studies demonstrate that successful deaminative functionalization relies not only on outcompeting the H-atom transfer to the incipient radical but also on the generation of polarity-matched, productive chain-carrying radicals that continue to react efficiently. The overall implications of this technology for interconverting amine libraries were evaluated via high-throughput parallel synthesis and applied in the development of one-pot diversification protocols.
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