Tricarbonylchromium Phenyloxazoline and -Imine Complexes: Highly Regioselectiveortho-Additions of Carbon Nucleophiles

Application of a Planar Chiralη5-Cyclopentadienylrhenium(I)tricarbonyl Complex in Asymmetric Catalysis: Highly Enantioselective Phenyl Transfer to Aldehydes

“…Our synthesis of 3 started from cyrhetrenyl carboxylic acid 4 , which was obtained in a straightforward manner from [Re 2 (CO) 10 ] and cyclopentadienyl carboxylic acid following an excellent, high‐yielding procedure published by Jaouen et al13 The cyrhetrenyl oxazoline 6 14 was synthesized in an analogous manner to the corresponding ferrocene derivatives via amide 5 , which was cyclized using the Appel protocol (Scheme ) 15. Directed ortho ‐metalation16 of 6 using n BuLi in diethyl ether17 and subsequent quenching of the resulting lithiated species with benzophenone led to diastereomeric products in a ratio of 9:1 in favor of the product with S , R p configuration 18. All transformations give good to excellent yields, and the compounds are crystalline and stable to air, light, and moisture 14…”

Synthesis, properties, and reactions with C-nucleophiles of (phenyloxazoline)-, (phenylmethanimine)-, and (benzaldehyde hydrazone)tricarbonylchromium(0) complexes

“…t-BuLi (1.4 M in ether, 0.437 mL, 0.61 mmol) was added to a solution of complex la (160 mg, 0.51 mmol) in THF (5 mL) at -78 °C. The solution was slowly warmed to -20 °C over 3 h. After recooling, oxidation, and workup, GC analysis showed a single product and unreacted 4a (initial T 100 °C, initial time 5 min, 20 °C/min; Rf 13.6 min). Purification by flash chromatography (Si02,5/1 hexane/ether) afforded 35 mg (30%) of 39a, with a slight impurity of 4a.…”

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

“…736 Nucleophilic additions to monocyclic aromatic systems can be accomplished by formation of a tricarbonylchromium complex (Scheme 177). [737][738][739][740] With heterocyclic analogs, such as pyridyl, that undergo nucleophilic additions more readily than phenyl, the transition metal complex is not required (Scheme 178). [741][742][743][744][745][746] The methods described above can also be augmented by use of the oxazoline unit to direct lithiation reactions in the precursor aromatic system and the subsequent reactions with electrophiles.…”