Copper-Catalyzed Silylcupration of Activated Alkynes

Abstract

A highly efficient catalytic silylcupration of activated alkynes is reported. Upon reaction with silylboronates and methanol in THF at room temperature in the presence of copper(I) fluoride tris(triphenylphosphine), a range of ynamides and propiolates were found to undergo a smooth silylcupration. This reaction, which tolerates various functional groups, affords a straightforward and efficient entry to the corresponding β-silylenamides and -acrylates, which were formed with high levels of regio- and stereoselectivities.

Activation of the Si–B interelement bond related to catalysis

“…(1) syn-addition of the copper-based silicon nucleophile occurs with esters and amides, generating the E-configured products whereas (2) aldehyde and ketone derivatives form allenolate intermediates which are protonated opposite to the sterically demanding silyl group, eventually leading to Z-configured products. Similar work was later reported by Loh 103b and Evano 38 (Scheme 82, bottom).…”

“…A general and efficient procedure for the copper-catalysed addition of silylboronic esters to ynamides was demonstrated by Evano and co-workers in 2016 (65 -E-66; 67a-g -E-68a-g or E-69a, Scheme 22). 38 This mild protosilylation of ynamides gives access to various enamides with high regio-and stereocontrol. It is noteworthy that a single isomer was formed exclusively which has been attributed to a directing effect of the amide group.…”

Copper‐Catalyzed One‐Pot Borylative Aldolisation β‐Fluoride Elimination for the Formal Addition of Acrylates to Carbonyl Moieties

“…To develop this new approach, we first focused on the domino borylation/aldolisation step by using 4‐ t Bu‐benzaldehyde as a model substrate (Table ). As a starting point, we applied the conditions we previously described for catalytic alkyne borocupration by using 2 mol % of the copper catalyst CuF(PPh 3 ) 3 ⋅2 MeOH ( 5 ), 2 mol % of ( rac )‐BINAP ( L1 ), 1.2 equivalent of diboron 3 in THF or toluene at room temperature (entries 1 and 2).…”

Rhodium-Catalyzed Highly Regioselective and Stereoselective Intermolecular Hydrosilylation of Internal Ynamides under Mild Conditions

“…Rh­(I) was first employed to catalyze this hydrosilylation (Table , entries 1–3). Only the neutral catalyst [Rh­(CO) 2 Cl] 2 worked efficiently at room temperature to afford the desired β-silyl ( Z )-enamide 3a with a good regio- and stereoselectivity . The cationic catalyst [Rh­(COD) 2 ]­BF 4 failed to mediate the reaction well.…”

“…Both yields and stereoselectivities could be increased for alkyl-substituted ynamides ( 1k and 1l ). Noticeably, although β,β-disilylated enamide was unstable, the reaction still occurred for triisopropylsilyl (TIPS)-substituted ynamide at mild conditions. It provided a unique way to access β,β-disilylated enamide, which was usually hard to prepare under other harsh conditions.…”