Silver-Catalyzed Carboxylative Cyclization of Primary Propargyl Alcohols with CO₂

Abstract

By using silver complexes with bulky ligands such as DavePhos or N-heterocyclic carbenes, propargylic alcohols are smoothly converted with CO2 into a unique class of unexplored cyclic alkylidene carbonates. These systems, for the first time, also achieve the direct carboxylative cyclization of primary propargylic alcohols. The silver-DavePhos catalyst is further applied for the bis-carboxylative cyclization of primary propargyl derivatives, thereby providing an effective route to a series of previously inaccessible and industrially relevant α-alkylidene cyclic carbonates.

Liquid‐liquid‐phase Synthesis of exo‐Vinylene Carbonates from Primary Propargylic Alcohols: Catalyst Design and Recycling

“…Taking propargyl alcohol as a model substrate and XPhos as the hydrophobic ligand, silver(I) salts of varying lipophilicity, including Ag‐neodecanoate (AgOC 10 ), ‐stearate (AgOC 18 ) and ‐cyclohexanebutyrate (AgOC 4 Cyc), were tested in the catalytic reaction at 1 mol% loading. We expected that modifying the silver carboxylate additive would result in only minor differences in basicity – a critical parameter according to our previous investigations – across the series [4] . This is supported by the observation that remote modifications in the carboxylate structure does not induce significant changes to the pK a of the respective conjugate acid (pK a (H 2 O, 25 °C) acetic acid=4.76; cyclohexylbutyric acid=4.93; valeric acid=4.82) [15] .…”

“…This is supported by the observation that remote modifications in the carboxylate structure does not induce significant changes to the pK a of the respective conjugate acid (pK a (H 2 O, 25 °C) acetic acid=4.76; cyclohexylbutyric acid=4.93; valeric acid=4.82) [15] . With this assumption, we also expected the stability of the catalyst resting state (Ag(PCy 2 R)(OOCR 2 ) to be similar to that observed for AgOAc, which proved to be thermally robust during recycling experiments [4] . Indeed, full conversions and selectivities of ≥95 % towards the desired EVC ( A ) were obtained for all silver(I) salts tested (entries 1–4).…”

“…demonstrated for the first time the superior reactivity and regioselectivity offered by bis‐ exo ‐vinylene carbonates (bis‐EVCs) in the reaction with diamines (poly(urethane)s, PUs) or diols (poly(carbonate)s) [3] . Inspired by this work, our group contributed a flexible and economic synthesis of new and previously inaccessible bis‐EVCs using 1,4‐butynediol as a building block [4] . We subsequently applied this methodology to the preparation of monomers based on commercially available epoxides/1,4‐butynediol, which were used to access new poly(urethane)s and poly(carbonate)s [5] .…”

“…We have shown that the conversion of primary propargylic alcohols to unsubstituted EVCs – unattainable using previously reported catalytic systems – can be achieved by using Buchwald‐type phosphine ligands or the N‐heterocyclic carbene ligand IPr paired with AgOAc [4,13] . We attempted to deliver a immobilised system on solid supports, incorporating these catalyst requirements (see SI section 2).…”

Green Synthesized AgNPs Embedded in COF: An Efficient Catalyst for the Synthesis of 2‐Oxazolidinones and α‐Alkylidene Cyclic Carbonates via CO2 Fixation

“…[49][50][51][52] But all the reported catalysts were employed under homogeneous reaction conditions whereas our catalyst can perform the reaction under heterogeneous condition, hence recyclability and reusability of the catalyst offers added advantages. Earlier several methodologies have been published for the catalytic synthesis of α-alkylidene cyclic carbonates through CO 2 fixation by silver metal-containing catalysts, [53][54][55][56][57][58][59][60] The main drawbacks of those catalytic protocols are: use of high CO 2 pressure; [53,56,[59][60] requirement of non greener solvent; [54][55][56][57][59][60] homogeneous catalytic condition; [55,57,58,60] large reaction duration etc. Here our catalytic system worked under 1 bar CO 2 pressure, at room temperature and solvent free heterogeneous reaction conditions.…”