Synthesis of Biarylazacyclooctynone (BARAC) Derivatives by Deprotonation of Enol Triflates

摘要

Strain-promoted azide-alkyne cycloaddition (SPAAC) is a reliable reaction to connect cycloalkynes and azides specifically. The reaction proceeds without toxic copper salts due to the high reactivity of cycloalkynes, compared to the conventional Huisgen cycloaddition using acyclic acetylenes. Among the various cyclooctyne derivatives for SPAAC, Bertozzi has reported biarylazacyclooctynone (BARAC) has the highest rate constant in the cycloaddition with azides. However, the preparation of BARAC derivatives needs multi-step synthesis and a practical method has been required for biochemical applications in the synthetic community.