A pure ruthenium hydride complex with N-heterocyclic carbene (NHC) ligand was efficiently generated from the reaction of a second-generation Grubbs ruthenium catalyst with vinyloxytrimethylsilane and unambiguously characterized. This ruthenium hydride complex showed high catalytic activity for the selective isomerization of terminal olefin and for the cycloisomerization of 1,6-dienes. These reactions of N-allyl-o-vinylaniline lead to novel synthetic methods for heterocycles such as indoles and 3-methylene-2,3-dihydroindoles, which are useful synthons for bioactive natural products. These procedures address an important issue in diversity-oriented synthesis.
Transition-metal-catalyzed cyclization of a,w-dienes is an efficient method for the construction of carbo-and heterocycles. One particularly interesting cyclization is olefin metathesis, [1] in which significant progress was made after the development of well-defined ruthenium-carbene catalysts, such as A and B (Scheme 1). In particular, the commercially available ruthenium-carbene catalyst B has shown enhanced activity in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), and cross metathesis (CM). [1c, 2] On the other hand, the nonmetathetic behaviors of ruthenium-carbene catalysts have been demonstrated in recent studies of olefin metatheses.[3] When a substrate cannot give a product by metathesis, nonmetathetic reactions, such as the Kharasch addition, [4] olefin isomerization, [5] and hydro-
Non-metathesis reactions of ruthenium carbene catalysts, such as olefin isomerization, hydrogenation, radical reaction, activation of silane, cyclopropanation, epimerization cocyclopropane, [3 + 2] cycloaddition, and cycloisomerization, are summarized. The utility of these reactions was demonstrated by the synthesis of indole using olefin isomerization and subsequent ring-closing metathesis, the synthesis of indoline using cycloisomerization, and the synthesis of the putative structure of fistulosin using cycloisomerization as a key step.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.