An Organocatalytic Route to endo‐Vinylene Carbonates from Carbon Dioxide‐Based exo‐Vinylene Carbonates

Abstract

An organocatalytic route has been developed for the isomerization of exo‐vinylene carbonates (exo‐VCs) to endo‐vinylene carbonates (endo‐VCs). The exo‐VC starting material can easily be obtained from propargylic alcohols via cyclization with carbon dioxide. In this study, these exo‐VCs are shown to isomerize to the thermodynamically more stable endo‐VCs in the presence of an N‐heterocyclic base and phenol. Density functional theory (DFT) studies were conducted to elucidate the mechanism, tackling difficulties of the description of charge separation steps. This isomerization process delivers an ample diversity of endo‐VCs in good to excellent yields and chemoselectivities under mild reaction conditions.

Boosting the Reactivity of Bis-Lactones to Enable Step-Growth Polymerization at Room Temperature

“…Mechanistically, after the first ring-opening upon addition of n -butanol (Figure c), the formation of 6b may result from a trans -lactonization of 6a involving the pendant enol moiety (before it tautomerizes into methyl ketone). A double proton shift between the pendant enol and exomethylene moieties of 6a is also conceivable, but it seems less likely as it involves an 8-membered transition state . Then, both 6a and 6b may react with a second molecule of n -butanol to give the double-addition product 7 .…”

“…A double proton shift between the pendant enol and exomethylene moieties of 6a is also conceivable, but it seems less likely as it involves an 8-membered transition state. 42 Then, both 6a and 6b may react with a second molecule of n -butanol to give the double-addition product 7 . The lower reactivity of the lactone with the endocyclic C=C double bond, as substantiated by its presence as a terminal group, may explain the low M w obtained.…”