Asymmetric dearomatization catalysed by chiral Brønsted acids via activation of ynamides

Synthesis of Axially ChiralN‐Arylindoles via Atroposelective Cyclization of Ynamides Catalyzed by Chiral Brønsted Acids

“…To date, rare examples on the formation of axial chirality based on ynamides were developed, except for the rhodium‐catalyzed enantioselective [2+2+2] cycloaddition of ynamides for the construction of C−N axially chiral anilines, as reported by Tanaka [10a] and Hsung, [10b] respectively. Inspired by these results and by our recent work on the chiral Brønsted acid (BA) catalyzed dearomatization reaction [11a] and kinetic resolution [11b,c] based on ynamides, we envisioned that chiral Brønsted acid‐catalyzed reaction of o ‐anilino ynamides preinstalled with a sterically demanding group might proceed via atroposelective 5‐ endo ‐ dig cyclization for the synthesis of C−N axially chiral indoles (Scheme 1c). Herein, we describe the realization of such a Brønsted acid‐catalyzed atroposelective 5‐ endo ‐ dig cyclization of o ‐anilino ynamides, leading to the practical and atom‐economic synthesis of valuable axially chiral indole frameworks in excellent yields with generally excellent enantioselectivities.…”

Modular approach to non-aromatic and aromatic pyrroles through gold-catalyzed [3 + 2] cycloaddition of 2H-azirines and ynamides

“…Moreover, the high synthetic potential of 3H-pyrroles, which have found application as hetero-dienes in the Diels-Alder reaction, has been convincingly proven. [21][22][23] In recent years, significant efforts have been made to construct 3H- [24][25][26][27][28] and 2H- 24,25,[29][30][31][32][33][34][35] pyrroles. Some of the reported synthetic schemes are based on the dearomatizations of 1Hpyrroles; typically, these reactions proceed under harsh conditions.…”

“…31,32 The cyclization of complex prefunctionalized substrates into 3H-and 2H-pyrroles requires a tedious assembly of the corresponding precursors. 29,34,35 To overcome these limitations, several modular synthetic methods have been proposed; however, they are either of a limited scope, 24,27,30 or employ inconvenient starting materials 25,26 (e.g., malodorous and toxic isocyanides 36 ). Considering all these data, one can conclude that the development of expedient modular protocols for the syntheses of these heterocycles comprises a challenging task.…”

“…In recent years, significant efforts have been made to construct 3 H - 24–28 and 2 H - 24,25,29–35 pyrroles. Some of the reported synthetic schemes are based on the dearomatizations of 1 H -pyrroles; typically, these reactions proceed under harsh conditions.…”

Efficient synthesis of tetracyclic γ-lactamsviagold-catalyzed oxidative cyclization of alkenyl diynes

“…Inspired by these results and by our recent study on developing ynamide chemistry for heterocycle synthesis, [12][13][14] we envisioned that the oxidative cyclopropanation might be achieved through catalytic oxidative cyclization of alkenyl N-propargyl ynamides 1, generating the corresponding cyclopropyl-substituted γ-lactams 2 (Scheme 1c). Nevertheless, it is challenging to realize this tandem reaction, because of two types of competing reactions.…”