Organocatalytic Trapping of Elusive Carbon Dioxide Based Heterocycles by a Kinetically Controlled Cascade Process

Abstract

A conceptually novel approach is described for the synthesis of six-membered cyclic carbonates derived from carbon dioxide. The approach utilizes homoallylic precursors that are converted into five-membered cyclic carbonates having a b-positioned alcohol group in one of the ring substituents. The activation of the pendent alcohol group through an Nheterocyclic base allows equilibration towards a thermodynamically disfavored six-membered carbonate analogue that can be trapped by an acylating agent. Various control experiments and computational analysis of this manifold are in line with a process that is primarily dictated by a kinetically controlled acylation step. This cascade process delivers an ample diversity of six-membered cyclic carbonates in excellent yields and chemoselectivities under mild reaction conditions.

Recent developments in organocatalysed transformations of epoxides and carbon dioxide into cyclic carbonates

“…An interesting piece of work was published by Kleij et al in 2020, reporting the ability to convert five-membered cyclic carbonates into six-membered cyclic carbonates. 52 By synthesising alcohol-functionalised five-membered cyclic carbonates, it was discovered that these compounds could undergo an organocatalysed cascade reaction in the presence of the guanidine-superbase 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 1-acetylimidazole (AcIm). By first converting homoallylic alcohols into epoxides, followed by carbon dioxide insertion to form five-membered cyclic carbonates, the desired compounds could be isolated via an induced isomerisation and selective acylation route (Scheme 12).…”

Recent progress in the catalytic transformation of carbon dioxide into biosourced organic carbonates

“…[1][2][3][4][5][6][7][8] The most common way to prepare such carbonates is through the coupling of epoxides and CO 2 , [9][10][11] a reaction that has reached a high level of sophistication thanks to the development of improved catalysts, [12][13][14][15][16] and new concepts. [17][18][19] A more recent trend shows a shift towards the use of biosourced feedstock in the synthesis of organic carbonates, i.e., so-called bio-carbonates. These biosourced carbonates are believed to give new impetus for the development of a variety of new applications such as their use as drop-in monomers for sustainable polymers, 20,21 the creation of isocyanate-free polyurethanes (NIPUs), 22,23 new types of plasticizers, 24 green and biodegradable solvents and surfactants, 25 and functionalized building blocks for organic synthesis.…”

Photocatalytic Synthesis of Substituted Cyclic Carbonate Monomers for Ring‐Opening Polymerization

“…In a more recent approach, our group demonstrated that tri-substituted 6MCCs can be obtained from 5MCCs that comprise of β-positioned (exo-cyclic) alcohol groups that upon activation by base allow for an unusual isomerization process (Scheme 1b). [11] In this latter approach, it was necessary to protect the alcohol group of the 6MCC product to prevent backequilibration to the thermodynamically more stable 5MCC. Preliminary ROP experiments with this type of 6MCC, however, were unsuccessful and inspired us to devise new synthetic methods to create different types of 6MCC monomers.…”