Cyclopropenes and methylenecylopropanes as multifunctional reagents in transition metal catalyzed reactions

Elementary Steps of Gold Catalysis: NMR Spectroscopy Reveals the Highly Cationic Character of a “Gold Carbenoid”

“…[9][10][11][12] To achieve this, recourse was taken to the rearrangement of the 3,3-disubstituted cyclopropenes 3 a-d (see below), which is known to constitute an excellent entry into metal carbene chemistry in general. [13] Building on the pioneering studies of Binger et al, [14] this transformation allowed the synthesis of a host of well-defined carbene complexes of transition metals as different as Ti, Co, Zr, Ru, Ta, W, Re, and Os. [14][15][16] Most notably, it opened the very first route to the now-classical Grubbs ruthenium carbene catalysts [(R 3 P) 2 Cl 2 Ru = CH À CH = CPh 2 ] (R = Ph, Cy (cyclohexyl)) for olefin metathesis.…”

“Cut and Sew” Transformations via Transition-Metal-Catalyzed Carbon–Carbon Bond Activation

“…7 Early work of TM-catalyzed C–C activation of ACPs was reported by Noyori, Schuchardt, Trost and Tsuji. 8 Based on different metal catalysts applied, two modes of activation with ACPs are possible: palladium and rhodium prefer to insert into the distal C 3 –C 4 bond via oxidative addition, whereas ruthenium and nickel tend to cleave the proximal C 2 –C 3 bond through two plausible intermediates 1 and 2 (Scheme 2).…”

Development of New Cycloaddition Reactions Based on the Unique Reactivity of Unsaturated Hydrocarbons

“…While the unsubstituted methylenecyclopropane cyclodimerized in the presence of a Ni catalyst (Chart 22), [36][37][38][39] few examples have been reported for the cyclodimerization of substituted methylenecyclopropanes. [40][41][42] We carried out the reaction of an electron-deficient methylenecyclopropane 39 (ethyl cyclopropylideneacetate) in the presence of Ni(cod) 2 -PPh 3 and observed the formation of cyclodimers such as 40-43 (Table 5).…”

“…The [3ϩ2] cycloaddition generally proceeded, and the formation the cyclopentane derivative was observed (Chart 25). [40][41][42] The high and unique reactivity of 39 prompted us to investigate the cross coupling reaction of 39 with various unsaturated hydrocarbons. The Ni-catalyzed reaction of 39 with alkenes gave the expected [3ϩ2] cycloadduct in good yields (Chart 26).…”