Silver(I)‐Catalyzed Hydroazidation of Ethynyl Carbinols: Synthesis of 2‐Azidoallyl Alcohols

Abstract

The hydroazidation of alkynes is the most straightforward pathway to synthetically useful vinyl azides. However, a general hydroazidation of alkynes remains elusive. Herein, a chemo- and regioselective transformation of ethynyl carbinols into vinyl azides is described. This reaction produces a wide variety of 2-azidoallyl alcohols with high efficiency and in good to excellent yields. These compounds constitute a new class of densely functionalized synthetic intermediates. Their synthetic potential has been demonstrated by further transformations into NH aziridines. The mechanistic aspects of the reaction will attract the attention of chemists working on alkyne chemistry and silver catalysis. The findings that are described in this paper represent significant advances in the regioselective hydroelementation of alkynes and open a new reaction manifold for exploitation.

DFT studies on the mechanism of Ag2CO3‐catalyzed hydroazidation of unactivated terminal alkynes with TMS‐N3: An insight into the silver(I) activation mode

“…The activation barriers of these three cases catalyzed by one to three water is higher than that of TS7 (8.2 kcal/mol) by 18.3–25.7 kcal/mol (Supporting Information Figure S9). Thus, the hydrogen sources of the C2 atom mainly come from AgHCO 3 and partial from water, which is in accordance with the experimental finding . Thereby, the above results implied that the presence of silver‐acetylide species and Ag + /π coordination interaction beween Ag + and triple bond of A can efficiently improve the formation of vinyl azide in comparison with only water‐assisted cases.…”

“…Accordingly, the development of practical synthetic methods for the convenient preparation of newly functionalized vinyl azides is still highly appealing. Recently, Bi et al reported the first chemo‐ and regioselective hydroazidation of ethynyl carbinols to vinyl azides by Ag 2 CO 3 catalysis (Scheme ) . This represented a significant advancement for achieving regioselective hydrofunctionalization of alkynes.…”

“…Moreover, the reaction mechanism for silver‐catalyzed transformation and the general reaction mode of silver salts remains little understood compared to that for the gold‐catalyzed reaction, partially because the lack of the isolable organosilver intermediate . As a part of our continued efforts toward understanding the mechanism of silver(I)‐catalyzed C–heteroatom bond formation reactions, we became interested in the title reaction reported by Bi group . Therefore, we conducted a detailed investigation of the mechanism for the Ag(I)‐catalyzed hydroazidation of unactivated ethynyl carbinols ( A , Scheme ) with TMS‐N 3 by density functional theory (DFT).…”

Recent Organic Transformations with Silver Carbonate as a Key External Base and Oxidant

“…Based on the results of these reactions, water must play an important role in the reaction. In 2014, the Bi group reported a Ag(I)-catalyzed hydroazidation to provide 2-azidoallyl alcohols 21 from ethynyl carbinols 20 (Scheme 15) [28]. Hydroazidation is one of the most attractive routes for synthesizing vinyl azides [29].…”

Silver‐Catalyzed Cross‐Coupling of Isocyanides and Active Methylene Compounds by a Radical Process

“…[15] Herein, we report anovel radical coupling/isomerization strategy for the C À Cc ross-coupling of isocyanides and active methylene compounds. [16] Theo ver-insertion of isocyanides,w hich is most frequently encountered in the transition-metal-catalyzed direct CÀHf unctionalization with isocyanides,c an be skillfully avoided by this strategy.D uring this manuscript preparation, Hong et al reported af ormal coupling/isomerization of isocyanides and benzyl cyanides, in which anew C À Cbond is formed indirectly by addition of acarboanion to an imidoyl copper intermediate (Figure 1b). [17] In our present work, the CÀCc oupling event directly occurs by ar adical addition process with the generation of an imidoyl radical intermediate (Figure 1c).…”