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 “CO2R” carrier, as it can selectively transfer the alkoxycarbonyl group to the alcohol and regenerate the amidine base.
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Carafa et al. (2011) studied this question.