DBU‐Promoted Nucleophilic Activation of Carbonic Acid Diesters

• Published in: European Journal of Organic Chemistry
• Main Authors: Carafa, Marianna, Mesto, Ernesto, Quaranta, Eugenio
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2011
• Subjects: Ketene; Carbonic acid
• Online Access: http://dx.doi.org/10.1002/ejoc.201001725; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fejoc.201001725; http://onlinelibrary.wiley.com/wol1/doi/10.1002/ejoc.201001725/fullpdf

Abstract The reactivity of carbonic acid diesters in the presence of the amidine base DBU (1,8‐diazabicyclo[5.4.0]undec‐7‐ene) has been investigated for the first time. Organic carbonates can be activated by DBU through the formation of N ‐alkoxycarbonyl ketene aminal 2 as the ultimate product. The latter species may form through deprotonation of the corresponding N ‐alkoxycarbonyl‐amidinium cation 1 + by the amidine base. We have for the first time isolated and characterized, both in the solid state (X‐ray crystal structure determination, IR) and in solution (NMR), a few 1 + chloride salts and studied their reactivity towards the organic base. The reactivity of both 1 + and 2 with methanol has also been explored. Ketene aminal 2 behaves as a “CO 2 R” carrier, as it can selectively transfer the alkoxycarbonyl group to the alcohol and regenerate the amidine base.