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Updated: Aug 7, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Mild and nonracemizing conditions for Ullmann-type diaryl ether formation between aryl iodides and tyrosine
1State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China.
Abstract:
CuI/N,N-dimethylglycine-catalyzed coupling reaction of L-tyrosine derivatives and L-phenylalanine-derived iodides in the presence of Cs2CO3 works at 90 degrees C to provide the corresponding diaryl ether. Partial racemization occurs when N-Boc- and N-Cbz-protected aromatic amino esters are used, while N-trityl- and N,N-dibenzyl-protected aromatic amino esters give rise to coupling products without loss of optical purity. Little racemization is also observed in cases of N-Boc- and N-Cbz-protected aromatic amino acids as substrates. But their reaction yields are moderate. On the basis of these studies, shorter protocols for assembling (S,S)-isodityrosine and K-13 are developed.
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