Ruthenium‐Catalyzed Cyclopropanation

Pd-Catalyzed Heck-Type Cascade Reactions with N-Tosyl Hydrazones: An Efficient Way to Alkenes via in Situ Generated Alkylpalladium

“…Since the discovery of transition-metal-catalyzed asymmetric cyclopropanation of alkenes with diazo compounds in the 1960s, various useful transformations involving active metal–carbene intermediates have been discovered, which played an important role in the revolution of modern organic synthetic methods . In contrast to the well-documented rhodium-, copper-, and ruthenium-catalyzed reactions, palladium-catalyzed transformations that involve Pd carbene intermediates so far have received less attention.…”

Ruthenium-Catalyzed Cycloadditions to Form Five-, Six-, and Seven-Membered Rings

“…Hence, the recently reviewed topic of ruthenium-catalyzed alkyne–azide “click” cycloadditions is not covered. − Reactions that are stoichiometric in ruthenium or exploit ruthenium as a Lewis acid (and do not proceed by way of intermediates that possess carbon–ruthenium bonds) are not covered. This includes dehydrogenative annulations that occur through successive condensation − and photochemically promoted ruthenium-catalyzed cycloadditions. − Ruthenium-catalyzed cyclopropanations − and (2+2) cycloadditions − have been reviewed elsewhere and are not covered.…”

CpRuCl(PPh3)2-Catalyzed Cyclopropanation of Bicyclic Alkenes with Tertiary Propargylic Acetates

“…So far, these metal catalysts proved efficient for the cyclopropanation of electron-rich alkenes; in contrast, palladium catalysts are preferred for the reactions involving electron-deficient as well as strained alkenes . Ruthenium catalysts were recognized in the early 1990s 3 as a cheaper alternative to the more expensive rhodium catalysts with promising results in the area of enantioselective cyclopropanation. 3c,d, The ruthenium-catalyzed cyclopropanation of strained bicyclic alkenes such as norbornene 1 pose problems. Usually, in the presence of ruthenium carbene species generated from diazo compounds, norbornene leads to the ROMP (ring-opening metathesis polymerization) via the formation of ruthenacyclobutanes as intermediates .…”