STERIC CONSEQUENCE OF THE DIASTEREOSELECTIVE ADDITION OF CHIRAL LITHIUM 2-(1-DIMETHYLAMINOETHYL)PHENYL CUPRATES TO SOME ENONES

Article abstract of DOI:10.1016/0022-328X(86)80016-X

Conjugate addition of the mixed chiral species lithium ((S)-2-(1-dimethylaminoethyl)phenyl)(2-thienyl)cuprate to (E)-4-phenyl-3-buten-2-one, 2-cyclohexenone or to 2-cyclopentenone proceeds with high diastereoselectivity.The first two enones gave crystalline adducts directly, while the non-crystalline cyclopentenone adduct was converted into a crystalline methiodide.The crystal structures of the compounds have been determined from single-crystal X-ray diffractometer data in order to reveal the configurations at the new chiral centers.In all three cases the configuration at the new asymmetric centre is S. (S,S)-4-(2-(1-Dimethylaminoethyl)phenyl)-4-phenyl-2-butenone, C20H25NO, crystallizes in space group P21 with a 7.604(2), b 9.398(5), c 12.290(6) angstroem, β 92.30(3) deg and Z=2.Full-matrix least-squares refinement of 273 structural parameters gave R=0.066 for 1015 observed independent reflections. (S,S)-3-(2-(1-dimethylaminoethyl)phenyl)-2-cyclohexanone, C16H23NO crystallizes in space group P212121 with a 12.499(4), b 6.645(3), c 17.568(7) angstroem and Z=4.Full-matrix least-squares refinement of 142 structural parameters gave R=0.068 for 1507 observed independent reflections.(S,S)-1-(2-(3-Oxocyclopentyl)phenyl)ethyltrimethylammonium iodide, C16H24NOI, crystallizes in space group P41, with a 10.569(3), c 30.895(7) angstroem and Z=8; there are thus two crystallographically independent cations in the asymmetric unit.Full-matrix least-squares refinement of 342 structural parameters gave R=0.054 for 2119 observed independent reflections.The (S,S)-configuration observed in these adducts indicates that the conjugative addition gives the least crowded lithium enolate as the major product.