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.

An asymmetric carbenoid insertion into S-H bonds catalyzed by copper-chiral spiro bisoxazoline complexes has been developed, in which a series of alpha-mercaptoesters were produced in high yields with moderate to good enantioselectivities (up to 85% ee); this result represents the best enantioselectivity in the catalytic asymmetric carbenoid S-H bond insertion reaction.

A copper-catalyzed asymmetric O-H insertion of a-diazo phosphonates with alcohols by using chiral spiro bisoxazoline ligands was developed. The insertion reaction exhibited good yields (up to 89%) with high enantioselectivities (up to 98% ee) and provided an efficient approach for synthesis of enantiomerically enriched a-alkoxy and hydroxy phosphonate derivatives starting from readily available materials.Enantiomerically enriched a-functionalized phosphonate derivatives are important building blocks for biologically active compounds, particular for pharmaceuticals. The development of efficient and enantioselective methods for preparation of a-functionalized phosphonates is of high value and has drawn increasing attention. 1 Transitionmetal-catalyzed asymmetric O-H bond insertion reaction of a-diazo phosphonates provides an convenient approach to chiral a-alkoxy and hydroxy phosphonate derivatives. 2 Although the copper-and iron-catalyzed asymmetric O-H insertions of a-diazo esters with alcohols, phenols, and even water have been accomplished with excellent enantioselectivities by Fu's group 3 and our group, 4 the enantioselective O-H insertions of a-diazo phosphonates have not been explored yet, 5 partially due to high stability of adiazo phosphonates. 6 As a part of our continuous efforts on the transition-metal-catalyzed asymmetric heteroatom-hydrogen bond (X-H, X = N, O, S, Si, etc.) insertion reactions, 7 we here report a copper-catalyzed asymmetric O-H insertion of a-diazo phosphonates with alcohols by using chiral spiro bisoxazoline ligands 1 (Scheme 1). The O-H insertion reaction exhibited good yields (up to 89%) with high enantioselectivities (up to 98% ee). To the best of our knowledge, this is the first enantioselective X-H insertion reaction of a-diazo phosphonates.In the initial study, the insertion reaction of dimethyl diazo(phenyl)methylphosphonate (2a) with n-butanol (3a) was performed in dichloromethane at 25°C in the presence of 5 mol% catalyst generated in situ from CuCl, (S a ,S,S)-1a, and NaBAr F 8 (Table 1). To our delight, the reaction ran smoothly and afforded the desired O-H insertion product, dimethyl butoxy(phenyl)methylphosphonate (4aa) in 76% yield with 73% ee (Table 1, entry 1).

A carbene insertion into electron‐deficient C−H bonds of 1,3‐diesters, β‐ketoesters, β‐ketonitriles, and malononitriles was realized by using CuCN/PCy3 as the catalyst. The reaction provides a straightforward approach to the synthetically important multi‐substituted succinic acid derivatives. A plausible reaction mechanism with cyclopropanation/ring opening as key steps was proposed based on control experiments.

Enantioselective Copper-Catalyzed O-H Insertion of α-Diazo Phosphonates. -The asymmetric O-H insertion of α-diazo phosphonates with alcohols in the presence of a catalyst, generated in situ from a Cu(I) precursor, a chiral spiro bisoxazoline ligand and a sodium borate, provides good yields of α-alkoxy phosphonates with high enantioselectivities. The alkoxyphosphonates can be easily transformed to α-hydroxy phosphonates or α-hydroxy phosphonic acids. For example, compound (VI) is converted into α-hydroxy phosphonate (VII) in high yield and with conservation of the enantiomeric excess. -(ZHU, S.-F.; CHEN, W.-Q.; ZHANG, Q.-Q.; MAO, H.-X.; ZHOU*, Q.-L.; Synlett 2011, 7, 919-922, http://dx.