Stereochemical Control of Reductions. 7. Reagent Hinges: Cis Reduction of β-Octalones by Internal Delivery of Chromium(II)

Article abstract of DOI:10.1021/jo00156a033

Δ^1,9-Octal-2-ones with angular substituents R have been synthesized and subjected to reduction conditions by employing the ethylenediamine complex of CrSO4 in aqueous DMF at 25 deg C.For R = Me, CH2OCH2OCH2CH2OMe, CH2OTHP, and COOMe negligible reduction was observed within 60 h, and starting materials were recovered in 60 percent yields.For R= CH2OH and COOH complete disappearance of starting material was achieved in 30-64 h, with isolation of ca. 40 percent of saturated ketone having exclusively cis stereochemistry.These results are interpreted in terms of precoordination of Cr(II) to the hydroxyl function, internal donation to yield a chelated organochromium intermediate, and stereoretentive hydrolysis to cis product.