Enantioselective iron-catalysed O–H bond insertions

Abstract

The ready availability, low price and environmentally benign character of iron mean that it is an ideal alternative to precious metals in catalysis. Recent growth in the number of iron-catalysed reactions reported reflects an increasing demand for sustainable chemistry. Only a limited number of chiral iron catalysts have been reported and these have, in general, proven less enantioselective than other transition-metal catalysts, thus limiting their appeal. Here, we report that iron complexes of spiro-bisoxazoline ligands are highly efficient catalysts for asymmetric O-H bond insertion reactions. These complexes catalyse insertions into the O-H bond of a wide variety of alcohols and even water, with exceptional enantioselectivities under mild reaction conditions. The selectivities surpass those obtained with other transition-metal catalysts. This study should inspire and encourage the use of iron instead of traditional precious metals in the development of greener catalysts for catalytic asymmetric synthesis.

Iron, ruthenium and osmium

“…47 QO group; the change in spin state to high-spin; and the concentration of the oxidising power on one iron atom. 64 Iron complexes of bis(imino)pyridine and related ligands continue to attract interest. 53 The synthesis of a rare monomeric iron(II) hydroxy complex, [Fe(Hdidpa)CH 3 CN(OH)] (PF 6 ) 2 , is made possible by the use of the terdentate pyridinediimine ligand didpa; this has an amine group in a flexible tail, which stabilises the hydroxy ligand via an intramolecular hydrogen bond.…”

Iron-Catalyzed Enantioselective Reactions Through the Use of Chiral Bipyridine-Containing Ligands

“…Indeed, iron is one of the most abundant metals on earth; it is inexpensive, environmentally benign, and relatively non-toxic in comparison with other metals. [1][2][3][4][5][6] The combination of a bipyridine ligand with an iron salt has been recently demonstrated by our group to be a very efficient catalyst for various highly enantioselective transformations. [7,8] This newly designed chiral complex represents a breakthrough in the field of asymmetric catalysis using iron complexes.…”

Methyl (R)-2-(2-chlorophenyl)-2-(3-nitrophenylsulfonyloxy)acetate

“…For related structures, see: Sun et al (2007); Andersen et al (2007). For the synthesis of Clopidrogel from sulfonyloxyacetic esters of (R)-2-(2-chlorophenyl)-2-hydroxyacetic acid, see : Bousquet & Musolino (1999); Castaldi et al (2003); Ema et al (2007); Zhu et al (2010). For halogen bonds, see: Bianchi et al (2004); Fourmigue (2009); Metrangolo et al (2005).…”

“…Sulfonyloxyacetic esters of (R)-methyl-2-(2-chlorophenyl)-2-hydroxyacetate are commonly used in the synthesis of Clopidrogel, an antiplatelet drug used in the prevention of strokes and heart attacks (sold in the United States under the brand name of Plavix) (Bousquet & Musolino, 1999;Castaldi et al, 2003;Ema et al, 2007;Zhu et al, 2010). The title compound, a promising intermediate for the synthesis of Clopidrogel, was obtained in two steps from (R)-2-(2-chlorophenyl)-2-hydroxyacetic acid (Bousquet & Musolino, 2003).…”