Iron-catalyzed addition of Grignard reagents to activated vinyl cyclopropanes

Abstract

A highly regioselective iron-catalyzed addition of branched primary, secondary or tertiary alkyl Grignard reagents to activated vinyl cyclopropanes is described, which likely proceeds by a direct addition mechanism as opposed to single electron transfer or an iron-allyl based process.

Elementary Steps of Iron Catalysis: Exploring the Links between Iron Alkyl and Iron Olefin Complexes for their Relevance in CH Activation and CC Bond Formation

“…Owing to this enigmatic behavior, we conjectured that this system provides an opportunity to study and eventually control iron-mediated C-H activation processes which may be of more general interest. [10][11][12][13] The bis(diisopropylphosphino)propane ligand (dippp) was chosen in accordance with literature to ensure the necessary solubility of 1 and its precursor complex 2; [2-7, 14, 15] at the same time, dippp is thought to balance the steric shielding of and the accessibility to the unsaturated iron center in 1. In any case, they should serve as valuable mechanistic probes for reactions in which low-valent iron species of unknown constitution are generated in situ by empirically optimized recipes.…”

“…[9] In this context, we planned to use the bis-ethylene complex 1 for further mechanistic investigations into iron catalysis (Scheme 1). [10][11][12][13] The bis(diisopropylphosphino)propane ligand (dippp) was chosen in accordance with literature to ensure the necessary solubility of 1 and its precursor complex 2; [2-7, 14, 15] at the same time, dippp is thought to balance the steric shielding of and the accessibility to the unsaturated iron center in 1. However, initial attempts to reduce complex 2 with activated magnesium or lithium sand in the presence of ethylene in analogy to the literature [2][3][4][5][6][7] gave erratic results.…”

The Evolution of Fe‐catalyzed Nucleophilic Activation of Acceptor‐substituted Vinyl‐ and Arylcyclopropanes

“…This development is still ongoing; however, the main focus has shifted a bit in the direction of C−H‐bond, rather than C−X‐bond, activation . In 2009, Fürstner and coworkers reported an interesting conjugate addition of alkylferrates to acceptor‐substituted VCPs with concomitant C−C‐bond cleavage (Figure ) …”

“…[17] In 2009, Fürstnera nd coworkers reported an interestingc onjugate addition of alkylferrates to acceptor-substituted VCPsw ith concomitant CÀCbond cleavage ( Figure 1). [18] Abstract:A cceptor-substituted vinyl-(VCP) and arylcyclopropanes (ACP) are reactive substrates for nucleophilic activation using Bu 4 N[Fe(CO) 3 (NO)] (TBA[Fe]). In this account, the application of this catalytic strategyi nt raceless allylic substitution,[ 3 + 2]-cycloaddition,a nd Cloke-Wilson rearrangement will be presented.A dditional information,d e-rived from detailed spectroscopic and theoretical investigations, is discussed.T hese resultsn ot only lead to ad eeper understandingo ft he reactivity of the catalyst in VCP and ACP activation, but also set the stagef or an ew type of catalyst activationu sing photochemical irradiation at 415 nm.…”

Katalyse und Totalsynthese: eine persönliche Zwischenbilanz

“…Angewandte Essays 8732 www.angewandte.de der erheblichen verbleibenden Unsicherheit ließen sich die bereits erwähnten niedervalenten Eisenkomplexe von uns auch als Katalysatoren für andere C-C-Verknüpfungen einsetzen. Dazu zählen die Ringçffnung von Vinlycyclopropanen, [74] eisenkatalysierte Alder-En-Reaktionen sowie eine Reihe von [4+2]-, [5+2]-und [2+2+2]-Cycloadditionen. [75] Olefinmetathese in der Synthese: Es war ein glücklicher Zufall, der mich meine unabhängige Forschung in Mülheim etwa zu dem Zeitpunkt beginnen ließ, als die Olefinmetathese anfing, die Praxis der organischen Synthese zu revolutionieren.…”