Organocatalytic Coupling of Bromo-Lactide with Cyclic Ethers and Carbonates to Chiral Bromo-Diesters: NHC or Anion Catalysis?

Jian-Bo Zhu, Xiaoyan Tang, Laura Falivene, Lucia Caporaso, Luigi Cavallo, Eugene Y.-X. Chen

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

In the presence of a N-heterocyclic carbene (NHC) in THF, Br-substituted l-lactide (Br-LA) unexpectedly undergoes exclusive coupling with THF to form a chiral ω-bromo-α-keto-diester. This coupling reaction is completely selective (in a precise 1:1 fashion), readily scalable (>20 g scale), and extremely efficient (with only 50 ppm of NHC loading). Other cyclic ethers and carbonates can also undergo similar coupling with Br-LA, thus offering a class of Br-functionalized chiral diesters with various functions and chain lengths. Combined experimental and computational studies led to a coupling mechanism that proceeds through an anion (bromide)-mediated catalytic cycle, rather than an apparent NHC-catalyzed cycle.
Original languageEnglish (US)
Pages (from-to)3929-3933
Number of pages5
JournalACS Catalysis
Volume7
Issue number6
DOIs
StatePublished - May 3 2017

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