The diastereoselective Meth-Cohn epoxidation of camphor-derived vinyl sulfones

Some camphor-derived vinyl sulfones bearing oxygen functionality at the allylic position have been synthesized and their nucleophilic epoxidation reactions under Meth-Cohn conditions have been explored. The γ-oxygenated camphor-derived vinyl sulfones underwent mildly diastereoselective nucleophilic epoxidation reactions, affording the derived sulfonyloxiranes in up to 5.8:1 dr. The observed diastereoselectivities were sensitive to the reaction conditions employed. In contrast, no stereoselectivity was observed in the nucleophilic epoxidation of the corresponding γ-oxygenated isobornyl vinyl sulfone. A tentative mechanism has been proposed to explain the origins of the diastereoselectivit

Aryl Germanes as Ligands for transition Polymetallic Complexes: Synthesis, Structure, and Properties

A series of new carbonyl dichromium complexes bearing aryl germanes as ligands were prepared using improved approaches. The thermal reaction of Cr(CO)6 (1) with Me3GeGePh3 (3) led to the formation of Me3GeGePh[(η6‐C6H5)Cr(CO)3]2 (3a). The lithiation of [(η6‐C6H6)Cr(CO)3] (2) with nBuLi followed by the addition of Me2GeCl2 (4) or ClGeMe2GeMe2Cl (5) gave Me2Ge[(η6‐C6H5)Cr(CO)3]2 (4a) and [(OC)3Cr(η6‐C6H5)]GeMe2GeMe2[(η6‐C6H5)Cr(CO)3] (5a), respectively. The molecular structures of 3a and 4a, in their crystal forms, were studied by X‐ray diffraction analysis. The crystals of oligogermane 3a have shown to undergo a fully reversible phase transition at 160 K without any sign of decomposition. The complexes synthesized were also studied by multinuclear NMR, IR and UV/Vis spectroscopy, DFT calculations and electrochemistry. The presence of a Cr(CO)3 group in a range of oligogermanes has shown to impact on the physical and chemical properties of the compounds

A New Asymmetric Synthesis of Tricarbonylchromium Complexes of <i>ortho</i>-Substituted Benzaldehydes

ortho-Substituted [Cr(CO)₃(benzaldehyde)] complexes are obtained via nucleophilic addition of alkyl- and aryllithium reagents to a [Cr(CO)₃(phenylmethaneimine)] complex followed by endo-hydride abstraction with triphenylmethyl cation. This sequence, when carried out with a [Cr(CO)₃(benzaldehyde SAMP hydrazone)] complex affords substituted derivatives (Me, Bu, Ph, vinyl) with high (≥97%) diastereoselectivity and, after hydrolysis, ortho-substituted [Cr(CO)₃(benzaldehyde)]((S)-1) complexes of high enantiomeric purity