A Strategy for the Synthesis of Well-Defined Iron Catalysts and Application to Regioselective Diene Hydrosilylation

Abstract

We report the development of a well-defined Fe catalyst and its application to the regio- and stereoselective 1,4-hydrosilylation of 1,3-dienes. To the best of our knowledge, this is the first example of accessing a characterized low-valent Fe catalyst by controlled reductive elimination from a readily accessible Fe precatalyst.

Iron‐Catalysed Chemo‐, Regio‐, and Stereoselective Hydrosilylation of Alkenes and Alkynes using a Bench‐Stable Iron(II) Pre‐Catalyst

“…[13] The iron(0) (pre-)catalyst was elegantly synthesised in situ by a ligand-initiated reductive elimination of an iron(II) complex, however the iron(II) precursor itself was still relatively unstable. Only limited substrate scope was disclosed and reaction times of up to 24 h and catalyst loadings of 5 mol% were required.…”

Synthesis, reactivity, and some photochemistry of ortho-N,N-dimethylaminomethyl substituted aryl and ferrocenyl pentamethylcyclopentadienyl dicarbonyl iron complexes

“…Since deprotonation at the 2-position of N,N-dimethylaminomethyl ferrocene with n-BuLi occurs without any diastereoselectivity [40], 10 was obtained as its racemic mixture. The phenyl analogue 11 was obtained by the same method, using (o-(N,N-dimethylaminomethyl)phenyl)lithium [41,42] as the lithium reagent, but in somewhat higher yield, as a yellow solid with a marked light sensitivity in solution.…”

“…Cp*Fe(CO) 2 I [38], (o-(N,N-dimethylaminomethyl)phenyl)lithium [41,42], and obromo(methoxymethyl)benzene [65] were prepared according to the literature methods, while other chemicals were obtained commercially and used without further purification.…”

Title Pages

“…Extending the theme of transition metal catalysis, applications of lowcost and 'friendly' iron is now a familiar theme and diverse in nature. Recently reported are, among others, an asymmetric transfer-hydrogenation of aryl ketones with a chiral iron(II) bis(isonitrile) complex 26 ; an iron-(or cobalt)-catalyzed asymmetric hydrosilylation of ketones with chiral bis(oxazoline) complexes 27 ; regioselective 1,2-hydrosilylation of 1,3-dienes with iron bis-(2-pyridylaldimine) complexes 28 ; an iron-catalyzed dehalogenation of aryl halides 29 ; and inexpensive routes to key N-heterocyclics (including indoles) via iron-catalyzed cyclodenitrogenation of azides 30 . Catalysis with osmium is less diverse, but it is worth mentioning, perhaps, the elusive 7-endo-cycloisomerization to 1,2-dihydro-3-benzoxepines which is far more efficient than under Ru-, Rh-or W-catalysis 31 ; note also the osmium equivalent of Noyori′s homogeneous asymmetric hydrogenation of ketones 32 , affording high enantioselectivities with astonishing TOF values up to 300,000 h -1 .…”