Aromatic and olefinic C-H alkenylation by catalysis with spirocyclic NHC Ru(IV) pincer complex.

Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development. In this article, we have explored the C(sp²)—H alkenylation activity with novel spirocyclic N-heterocyclic carbene (NHC)-based cyclometalated ruthenium pincer catalyst system, SNRu-X. After screening catalyst and condition, a high valent Ru(IV) dioxide (X = O₂) species has demonstrated superior reactivity in the catalytic alkenylation of aromatic and olefinic C-H bonds with unactivated alkenyl bromides and triflates. This reaction has achieved the easy construction of a wide range of (hetero)aromatic alkenes and dienes, in good to excellent yields with exclusive selectivity. Preliminary mechanistic studies indicate that this reaction may proceed through a single electron transfer (SET) triggered oxidative addition, by doing so, providing valuable complementary to classical alke-nylation reactions that are dependent on activated alkenyl precursors. [ABSTRACT FROM AUTHOR]