Silylium-Catalyzed Regio- and Stereoselective Carbosilylation of Ynamides with Allylic Trimethylsilanes

Abstract

The regio- and stereoselective carbosilylation of tosylynamides with allylic trimethylsilanes takes place under mild conditions in the presence of catalytic TMSNTf2 or HNTf2 to give (Z)-α-allyl-β-trimethylsilylenamides with good yields. Theoretical calculations show the activation of the C–C triple bond of the ynamides by the trimethylsilylium ion and formation of a β-trimethylsilylketenimonium cation. Further transformations of the products demonstrate the synthetic utility of this reaction.

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.…”

TMSOTf-Catalyzed [4 + 2] Annulation of Ynamides and β-(2-Aminophenyl)-α,β-ynones for the Synthesis 2-Aminoquinolines

“…Initially, the catalyst TMSOTf activates ynamide 2 giving a β-silyl keteniminium ion A. 20 Then the nucleophilic N-attack of ynone 1 on keteniminium ion A generates the vinyl−silicon intermediate B, which undergoes protodesilication to achieve enamine intermediate C. 15 Subsequently, an intramolecular cyclization of TMSOTf-activated ynone D 21 by a conjugate addition reaction occurs to produce intermediate E. 17 Protodesilication of intermediate E is followed by enol/ketone tautomerism leading to intermediate 3. Finally, the aromatiza-tion of intermediate 3 furnished the 2-aminoquinoline 4.…”

“…Based on the results, a postulated mechanism for this TMSOTf-catalyzed [4 + 2] annulation is depicted. Initially, the catalyst TMSOTf activates ynamide 2 giving a β-silyl keteniminium ion A . Then the nucleophilic N-attack of ynone 1 on keteniminium ion A generates the vinyl–silicon intermediate B , which undergoes protodesilication to achieve enamine intermediate C .…”