[Fp-.eta.1-(1-polycycloalkyl)methylidene]+ to [Fp-.eta.2-(1-homopolycycloalkene)]+ rearrangement. Carbon migration in iron(II) alkylidenes. A new route to stabilized bridgehead olefins

A 1-Norbornene Adduct of a Transition Metal and an Electrochemical Study of the Bridgehead Olefin Complex

“…A transition-metal binding approach, similar to what has been employed in benzyne chemistry, − could be one possible strategy to obtain stable precursors of these short-lived compounds for synthetic and mechanistic studies. While transition-metal complexes of larger bridgehead double bonds are known − or speculated to have formed in metal-mediated reactions, − the trapping of smaller, more reactive bridgehead double bonds remains much more problematic, especially since trapping must usually be competitive with dimer formation resulting from formal 2 + 2 cycloaddition reactions. Here we report a new method to prepare a transition-metal adduct of 1-norbornene that overcomes the problems associated with competitive trapping and also describe the unexpected electrochemistry of this new transition-metal adduct.…”

“…A transition-metal binding approach, similar to what has been employed in benzyne chemistry, [24][25][26][27][28][29] could be one possible strategy to obtain stable precursors of these short-lived compounds for synthetic and mechanistic studies. While transition-metal complexes of larger bridgehead double bonds are known [30][31][32][33][34][35] to have formed in metal-mediated reactions, [36][37][38] the trapping of smaller, more reactive bridgehead double bonds remains much more problematic, especially since trapping must usually be competitive with dimer formation resulting from formal 2 + 2 cycloaddition reactions.…”

Carbene insertion into transition metal–carbon bonds: a new tool for catalytic C–C bond formation

“…This concept has been applied to the synthesis of metal-stabilised bridgehead olefins in situ, while they are normally very unstable and undergo rapid dimerisation. 25 Carbene insertions for other metals have also been studied, but to a much lesser extent. Competitive CO and carbene migratory insertion of alkyl fragments has been studied for osmium complexes and it turned out that these insertions favour the carbene ligand.…”

Metal-Catalyzed [4 + 2 + 2] Cycloadditions: Cycloadducts of Substituted Norbornadienes and Their Opening with Zeise's Dimer

“…This proposed mechanism passes through the platinum complex of anti-Bredt intermediate A . Such transition-metal complexes of strained bridgehead olefins are known, and the transient occurrence of 1-norbornene is also strongly supported 4 …”