SYNTHESIS AND ALKYLATION OF CYCLIC ALPHA-SULFONIMIDOYL CARBANIONS - NONTRANSFERABLE CHIRAL CARBANIONIC LIGANDS IN COPPER-MEDIATED ENANTIOSELECTIVE CONJUGATE ADDITION

The cyclic sulfoximines 4a and 4b have been prepared from (+)-(S)-S-me thyl-S-phenylsulfoximine (1). Deprotonation of 4a and 4b and alkylatio n of lithiosulfoximines Li-4a and Li-4b gave alpha-alkyl substituted s ulfoximines 5a (89% de), 5b (90% de), 6a (greater than or equal to 98% de), 6b (greater than or equal to 98% de), 7b (greater than or equal to 98% de) and 8b (greater than or equal to 98% de). The configuration of 6b was determined by X-ray structure analysis. Consecutive treatme nt of 5b, 6b and 8b with BuLi and CF3CO2H gave epimers epi-5b (64% de) , epi-6b (89% de) and epi-8b (81% de). alpha,alpha-Dialkyl substituted sulfoximines 9 (greater than or equal to 98% de) and epi-9 (greater t han or equal to 98% de) were obtained by alkylation of Li-5b and Li-Gb . Conjugate addition of cuprates 11-14, containing the acyclic sulfoni midoyl carbanions Ia-c, to cyclohex-2-en-1-one gave ketones 15 and 16 in good yields but with low asymmetric induction (8-49% ee). However, conjugate addition of cuprates 19b, 20b, 21b and 22b, derived from the cyclic lithiosulfoximines Li-7b and Li-8b, to cyclopent-2-en-1-one, c yclohex-2-en-1-one and cyclohept-2-en-1-one gave ketones 15a-c, 23b an d 24b with good to high asymmetric inductions (77-99% ee) in good yiel ds. The bicyclic ketone 27 (79% ee) was prepared from cyclohex-2-en-1- one via 24b in three steps.