Organic Photoredox Catalyzed Direct Hydroamination of Ynamides with Azoles

Abstract

Disclosed herein is a photoinduced selective hydroamination of ynamides with nitrogen heteroaromatic nucleophiles. By using an organocatalytic photoredox system, a direct method to construct a diverse of (Z)‐α‐azole enamides from ynamides and pyrazoles, as well as triazoles, benzotriazoles, indazoles, and tetrazoles, is developed, thus providing a photocatalytically synthetic route to heterocyclic motifs common in medicinal agents. Based on the mechanistic studies, the hydroamination is postulated to operate via a mechanism in which the single‐electron oxidation of ynamide and the intermediacy of an alkyne radical cation, is responsible for the observed reactivity.

Cerium(IV)‐Mediated Carbon‐Carbon Bond Formation for the Synthesis of Spirodienone Lactams

“…Although the spirodienone lactam 35 was the major product formed in this reaction, the hydration products 36 and 37 were obtained in a non‐negligible amount. The formation of 36 and 37 was expected due to the well‐known hydration of ynamides to amide [42–44] . To improve the ratio of the desired compound 35 we screened different solvents (Scheme 11) and oxidation conditions (Scheme 12).…”

“…The formation of 36 and 37 was expected due to the well-known hydration of ynamides to amide. [42][43][44] To improve the ratio of the desired compound 35 we screened different solvents (Scheme 11) and oxidation conditions (Scheme 12). While in THF a complete decomposition of the starting material was observed, in DCM the reaction was selective in favour of the non-desired compound 37.…”

Catalytic intermolecular hydrofunctionalizations of ynamides

“…Recently, Deng and co-workers established a mild synα-hydroamination of ynamides with azoles enabled by visible light catalysis (Scheme 50). 97 β-adducts. Besides, 1H-and 2H-tetrazole could participate in this useful transformation as well.…”

“…Recently, Deng and co-workers established a mild syn -α-hydroamination of ynamides with azoles enabled by visible light catalysis (Scheme 50). 97 Visible light activation of photocatalyst [Mes-Acr-Me]ClO 4 (9-mesityl-10-methylacridinium perchlorate) produces its excited state [Mes-Acr-Me*] + . Subsequent reductive quenching by ynamides leads to ynamide cation radical Int-81 , which is trapped by pyrazole to afford α-amino vinyl radical Int-82 .…”

Divergent Functionalization of Alkynes Enabled by Organic Photoredox Catalysis

“…In comparison to alkenes, alkynes have significantly higher oxidation potentials (Figure 1C). These electrochemical properties also preclude the formation of vinyl radical cation 25,26 with most oxidants or the excited state of common photoredox catalysts. The excited state of acridinium-based photoredox catalysts possess high reduction potentials up to +2.21 V and exhibited excellent reactivity toward alkene or arene functionalization.…”