Cobalt-Catalyzed Silylcarbonylation of Unactivated Secondary Alkyl Tosylates at Low Pressure

Abstract

A catalytic preparation of silyl enol ethers from unactivated secondary alkyl tosylates is reported. An inexpensive cobalt catalyst is used under mild conditions with low pressures of carbon monoxide. Nucleophilic, anionic cobalt carbonyls facilitate the catalytic activation of a range of alkyl tosylates. The silylcarbonylation offers a practical approach to synthetically valuable silyl enol ethers from simple starting materials.

Cu‐Catalyzed Hydroxymethylation of Unactivated Alkyl Iodides with CO To Provide One‐Carbon‐Extended Alcohols

“…A key advance in this regard is the work of Alexanian and co‐workers on Co‐ and Mn‐catalyzed C(sp 3 )−X carbonylative C−C coupling reactions, which occur at milder conditions . The same group also recently reported an intriguing Co‐catalyzed, redox‐neutral silylcarbonylation process for alkyl triflates to produce silyl enol ethers . However, to our knowledge there has been no report of reductive carbonylation of C(sp 3 )−X substrates.…”

“…[8] Carbonylation reactions of C(sp 3 )ÀXe lectrophiles are significantly less common. [11] However,t oo ur knowledge there has been no report of reductive carbonylation of C(sp 3 )ÀXsubstrates. [9] Ak ey advance in this regard is the work of Alexanian and co-workers on Co-and Mn-catalyzed C(sp 3 )À Xc arbonylative CÀCc oupling reactions,w hich occur at milder conditions.…”

“…[14] Here,w er eport conditions that provide hydroxymethylation products from alkyl iodides with high selectivity. Use of CsF as the base afforded moderate yield, and use of NaO t Bu as the base or toluene as the solvent favored reduction of the alkyl iodide over carbonylation (entries [10][11][12]. Thepresence of the copper catalyst was necessary for successful reaction (entry 2).…”

Cu‐Catalyzed Hydroxymethylation of Unactivated Alkyl Iodides with CO To Provide One‐Carbon‐Extended Alcohols

“…[10] Thes ame group also recently reported an intriguing Co-catalyzed, redox-neutral silylcarbonylation process for alkyl triflates to produce silyl enol ethers. [11] However,t oo ur knowledge there has been no report of reductive carbonylation of C(sp 3 )ÀXsubstrates.…”

“…Activation of the alkyl iodide was significantly affected by the choice of hydrosilane.O nly trace conversion was observed with Et 3 SiH, while other more frequently used hydrosilanes in copper hydride chemistry provided slightly higher conversions (entries 7-9). Use of CsF as the base afforded moderate yield, and use of NaO t Bu as the base or toluene as the solvent favored reduction of the alkyl iodide over carbonylation (entries [10][11][12]. Decreasing the amount of catalyst to 5mol %d iminished the yield measurably (entry 13).…”