Oxoammonium Salt‐Mediated Vicinal Oxyazidation of Alkenes with NaN₃: Access to β‐Aminooxy Azides

Abstract

An approach to the vicinal oxyazidation of alkenes has been achieved under mild and transition metal-free conditions. This method utilizes NaN 3 as the azidation agent and 2,2,6,6tetramethylpiperidine-1-oxoammonium tetrafluoroborate (TEMPO + BF 4 À ) as the single-electron oxidant as well as the oxygen source. By using this protocol, various β-aminooxy azides were synthesized and several complex bioactive molecules were functionalized.

Decade Advances of NaN3 in Three‐component Reactions

“…The first part of this review mainly describe recent breakthroughs via reactions with alkenes. [2][3][4][5] The Zeng group [2] studied the electrochemical azidoiodination reactions of alkenes with IN 3 . This method avoided the direct use of this explosive reagent.…”

“…Zheng and co-workers [3] designed the radical difunctionalization of alkenes by using NaN 3 as N-radical source and TEMPO + BF 4 À (2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoro-borate) 3.1 as the oxidant. Under room temperature, NaN 3 was oxidized to the azido radical 3.2 via single-electron transfer by TEMPO + BF 4 À , which was simultaneously reduced to TEMPO.…”

Free Radicals in the Queue: Selective Successive Addition of Azide and N-Oxyl Radicals to Alkenes

“…The addition of C-, O-, and N-centered free radicals to CC bonds has developed into an important group of synthetic methods in recent years. − Usually, only one radical R• capable of addition to a CC bond is used in a radical difunctionalization reaction to achieve selectivity (Scheme a). It undergoes addition to an alkene to form the most stable of the two possible C-centered radicals, and this step determines the regioselectivity of the process. , The resulting C-centered radical is usually intercepted by a second R• radical − or by a stable reagent, the concentration of which should be high enough to exclude side processes. ,− Examples of such reagents include persistent radical TEMPO, O 2 , I 2 , unsaturated organic radical acceptors, or oxidants transforming radicals into carbocations for the following nucleophile addition . Difunctionalization reactions involving more than one radical that can attack a CC bond are relatively rare. − In this work, we propose a system in which two different reactive radicals (capable of attacking CC bonds) are generated: azide and N- oxyl.…”

1,2-Amino oxygenation of alkenes with hydrogen evolution reaction

“…Despite their excellent regioselectivity, expensive transition-metal catalysts and/or complex ligands have propelled the development of alternative approaches. To avoid the use of metal-catalyst, oxidation-induced strategy has recently served as another fascinating way to synthesize β-amino alcohols with sacrificial oxidants (including hypervalent iodines 9,20,21 , peroxides 22 , diazodicarboxylates 23 , fluor-containing oxidants 24,25 , TEMPO 26,27 , etc.). While these methods ensure efficient approaches, their compatibility with oxygen and nitrogen sources may be problematic.…”