Phosphine-catalyzed regio- and stereo-selective hydroboration of ynamides to (Z)-β-borylenamides

Abstract

We report a tri-n-butyl phosphine catalyzed regio- and stereo-selective hydroboration of ynamides to yield (Z)-β-borylenamides in good yields. Surprisingly, a formal cis addition to the triple bond was observed as...

Green and rapid acid-catalyzed ynamide skeletal rearrangement and stereospecific functionalization with anisole derivatives

“…On the basis of the above mechanistic studies, previous literature data 1–9 and our previous studies on ynamides, 10,12 d a plausible mechanism is drawn in Scheme 3. First, the Brønsted acid initiates the reaction process by providing a proton (H + ) source on the alkyne in the compound 4-methyl- N -(phenylethynyl-2- 13 C)- N -(2-(phenylethynyl)phenyl)benzenesulfonamide ( 1a′ ) to produce intermediate A .…”

“…1 However, there are many challenges and problems facing synthetic chemists due to its complementary reactivities under radical, 2 ionic or acidic, 2 f ,3 and transition-metal-catalyzed reactions 4 due to the biased carbon–carbon (α and β) triple bond directly bind to the nitrogen atom bearing an electron-withdrawing functionality, which results in higher reactivity, unwanted by-products, and issues with chemo-, regio-, and stereospecificity. 1–4 Various research groups (Sahoo, 1 c ,2 d , f ,5 Ye, 1 b , f ,2 b ,3 b , d ,4 a Evano, 2 a ,6 Hashmi, 7 and many others 8 ) have remarkably utilized ynamides in the construction of various heterocyclic compounds with the help of transition metals, Brønsted acids or additives, depending on the selection of the starting material and reaction conditions. 1–8 In particular, the key reaction intermediates generated in ynamide reactions are keteniminium 2 f ,3 with electrophilic reagents and ketenimine 4 c ,9 under thermal conditions or with nucleophilic reagents.…”

“…1–4 Various research groups (Sahoo, 1 c ,2 d , f ,5 Ye, 1 b , f ,2 b ,3 b , d ,4 a Evano, 2 a ,6 Hashmi, 7 and many others 8 ) have remarkably utilized ynamides in the construction of various heterocyclic compounds with the help of transition metals, Brønsted acids or additives, depending on the selection of the starting material and reaction conditions. 1–8 In particular, the key reaction intermediates generated in ynamide reactions are keteniminium 2 f ,3 with electrophilic reagents and ketenimine 4 c ,9 under thermal conditions or with nucleophilic reagents. In addition, metal carbenes are generated when using transition metals 4 c and other specific types of reactions, such as cyclization 1 a ,4 c and cycloadditions.…”

Recent Advances in Ligand-Controlled Regio- or Stereodivergent Transition-Metal-Catalyzed Hydroelementation (H[E]) (E = H, B, Si, Ge) of C–C Unsaturated Systems

“…In this transformation, since both the regio- and enantioselectivities of the catalysis are supposed to be influenced and determined by two different ligands, establishing a class of finely tailored and highly modular chiral ligands with metal precatalysts would be a key not only to achieve high regiodivergence and enantioselectivity, but also to understand the correlation between the ligands and those selectivity outcomes. Motivated by ligand-controlled divergent catalysis within transition-metal-complex systems, exploring readily accessible and modular organocatalysts, i.e., tertiary phosphines, 70 for potential divergent hydroelementation reactions of alkenes and alkynes would be a promising research task.…”

Two-component symmetrical diarylation of ynamides

“…[11][12][13][14][15][16][17][18][19][20][21][22] On the other hand, ynamides, a special class of N-substituted alkynes, are of particular interest due to their unique reactivity arising from the polarization of N-lone pair electrons. [23][24][25][26][27][28][29][30][31][32][33][34][35] The intermediates involved in this process, such as keteniminium ions, and metal carbenoids, are crucial for metal-catalyzed dicarbofunctionalization reactions; the process allows making tetrasubstituted enamides. 36 Given the importance of such enamides, development of pathways for the synthesis of substituted enamides attracts attention.…”