Substrate‐Controlled Product Divergence: Conversion of CO₂ into Heterocyclic Products

Abstract

Substituted epoxy alcohols and amines allow substrate‐controlled conversion of CO2 into a wide range of heterocyclic structures through different mechanistic manifolds. This new approach results in an unusual scope of CO2‐derived products by initial activation of CO2 through either the amine or alcohol unit, thus providing nucleophiles for intramolecular epoxy ring opening under mild reaction conditions. Control experiments support the crucial role of the amine/alcohol fragment in this process with the nucleophile‐assisted ring‐opening step following an SNi pathway, and a 5‐exo‐tet cyclization, thus leading to heterocyclic scaffolds.

Deciphering key intermediates in the transformation of carbon dioxide into heterocyclic products

“…2A (See Supplementary Methods 2-4, and Supplementary Table 1 for further details). Under the established reaction conditions, 24 the deuterated GLY (1) was exclusively converted into carbonate 5, which supports the occurrence of an intramolecular attack of the nucleophilic carbonate species 4 that is formed in situ. The formation of 3 via direct CO2 insertion into the epoxide 2 as a result of a classic intermolecular ring opening was not observed.…”

Triarylborane-Catalyzed Formation of Cyclic Organic Carbonates and Polycarbonates

“…Their catalytic activity is superior in terms of catalyst loading compared to most metal-free systems to date, but moderate temperatures are needed to achieve high TOF, and this means that such systems have more in common with established metal-containing catalysts. These data suggest that new metal-free synthetic approaches to CO 2 incorporation including more complex products via substrate controlled mechanistic divergence previously demonstrated by Al-centered catalysts 67 should be accessible using a borane-containing catalyst system. 11 B NMR studies provide evidence for insertion of CO 2 into the nucleophile−borane bond, in a similar way to FLP catalyst systems, and the CO 2 insertion product can be used directly as a catalyst for these reactions.…”

Cycloaddition of CO2 to epoxides by highly nucleophilic 4-aminopyridines: establishing a relationship between carbon basicity and catalytic performance by experimental and DFT investigations

“…67 Finally, we turned our attention to the use of epoxy amines 5m and 5n that, in the cycloaddition reaction with CO2 (Scheme 3C), could respectively afford either carbonates 6ma and 6na (by the "traditional" cycloaddition mechanism), or carbonates 6mb and 6nb by initial coordination of CO2 to the nitrogen atom and H-transfer to 4. 87,88 As in the case of epoxy alcohols 5k and 5l, we selectively obtained carbonates 6mb and 6nb (Figures S39, S40) under mild conditions (60 °C, 10 bar CO2 in MeCN) that were isolated in very high yields by using just 2 mol% 4. As far as we are aware, this was the first organocatalytic (and halogen-free) approach to the reaction in Scheme 3C.…”