Transition Metal Catalyzed Preparation of Grignard Compounds

Abstract

The “inorganic Grignard reagents”, in particular those of 1, have surprisingly been shown to be efficient homogeneous catalysts for the conversion of inactive chloroarenes and heteroarenes (via the aryl–iron intermediate 2) into the corresponding Grignard compounds. The aryl–Grignard compounds are starting materials for, among other things, the preparation of aryl boron acid esters, which serve as substrates for the technically important Suzuki coupling.

Synthesis and structure of 5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines

“…Formation of di-Grignard reagent from 7 did not proceed at all by the usual procedure, but was accomplished in a high yield by using a catalytic amount of FeCl 2 as reported by Bogdanović and Schwickardi [8]. Fe(acac) 2 similarly worked albeit slightly less efficient than FeCl 2 .…”

Iron-Catalyzed Carbometalation of Propargylic and Homopropargylic Alcohols

“…Common oxygen protecting groups, olefins and tertiary nitrogens appear well-tolerated. Furthermore, primary and secondary homopropargylic alcohols provide the corresponding homoallylic alcohols on treatment with methyl Grignard reagent (entries [9][10]12). In ongoing studies, we have found that the ironcatalyzed carbometalation can be extended to phenylation 5 (entries 11-12) and ethylation (entries 13-14).…”

Iron Catalysis in Synthetic Chemistry

“…It has a covalent-bond character between the Fe and Mg centers. Such an observation supported the idea that iron can remain covalently bonded to magnesium in [Fe(MgX) 2 ], the "Inorganic Grignard Reagent" (173,198). They found that finely dispersed Fe(0)* particles in THF dissolved slowly on treatment with an excess of nC 14 H 29 MgBr and the resulting solution catalyzed the crosscoupling reaction (Scheme 131).…”

“…Fürstner et al (199) proposed the formation of a low-valent ferrate complex as the active species for their cross-coupling reactions based on their experimental data and literature reports (173,198). At first, there was an in situ formation of [Fe ( II) (MgX) 2 ] (ferrate complex) and subsequently it was oxidatively added between the R-X bond.…”