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

Abstract

An operationally mild, ruthenium‐based photocatalytic protocol has been developed for the conversion of γ‐mono‐ and γ,γ‐disubstituted allyl carbonates in the presence of Umemoto's reagent to afford substituted six‐membered cyclic carbonates. Variation and diversification of the carbonate ring substitution provides access to new monomers useful in ring‐opening polymerization leading to polycarbonates with potentially tailored properties, as illustrated by comparative experiments using monomers with different pi‐stacking capabilities.

Synthesis of 1,3‐Dioxan‐2‐ones by Photo‐Aerobic Selenium‐π‐Acid Multicatalysis

“…The combination of these two factors presumably is the reason why oxidative cyclizations of primary homoallylic carbonic acid esters were not reported for other catalytic or stoichiometric systems. Instead, previous procedures predominantly predicated on the use of either stronger nucleophiles, such as carbonate anions, carbamates, phosphoric, and phosphonic acid esters, [3a,3h,3I,8a,13,14] or substrates that contain the carbonic ester group in a non‐primary homoallylic position [3g] . Against this background, the scope shown in Scheme 2 underscores the fact that the title procedure leads to reasonable reaction outcomes even with more difficult substrates.…”

“…As a tactical counter design, Cossy et al. employed allylic and homoallylic carbonates in which the olefinic double bond was pre‐activated by the presence of an acetate nucleofuge located at the allylic position opposite to the carbonate unit (Scheme 1C) [3g] . These precursors underwent stereoselective cyclization upon exposure to iron(III) or indium(III) Lewis‐acid catalysts.…”

“…The authors reported that an aryl group at the acetoxylated carbon atom (Scheme 1C, beige sphere) was indispensable for the transient formation of a resonance‐stabilized allylic cation intermediate, which was subsequently intercepted by the neighboring carbonate nucleophile. To showcase the synthetic value of their protocol, this technique was later exploited by the same research group in the total synthesis of diarylheptanoid (3 S ,5 S )‐alpinikatin [3g] . The high utility and versatility reflected by each of these and related methods [8] emphasize their immense potential in contemporary organic synthesis and thereby foreshadow the continuing need for complementary tactics to expeditiously access cyclic carbonic acid esters.…”

“…employed allylic and homoallylic carbonates in which the olefinic double bond was pre‐activated by the presence of an acetate nucleofuge located at the allylic position opposite to the carbonate unit (Scheme 1 C). [3g] These precursors underwent stereoselective cyclization upon exposure to iron(III) or indium(III) Lewis‐acid catalysts. The authors reported that an aryl group at the acetoxylated carbon atom (Scheme 1 C, beige sphere) was indispensable for the transient formation of a resonance‐stabilized allylic cation intermediate, which was subsequently intercepted by the neighboring carbonate nucleophile.…”

“…To showcase the synthetic value of their protocol, this technique was later exploited by the same research group in the total synthesis of diarylheptanoid (3 S ,5 S )‐alpinikatin. [3g] The high utility and versatility reflected by each of these and related methods [8] emphasize their immense potential in contemporary organic synthesis and thereby foreshadow the continuing need for complementary tactics to expeditiously access cyclic carbonic acid esters.…”