Conjugate cuprate additions

Conjugate additions. Cuprate addition to ynoate esters and trapping with aldehydes (in the presence of EtjAlCl) provide special analogs of Baylis-Hillman reaction products. Trapping with phosphonoacetatic esters is another synthetically valuable variation. Silyl ketene acetals derived from 1,6-addition to allyl alk-4-yn-2-enoates undergo Claisen... 

The methodology used in the preparation of RU 486 (84) and other ll -steroids is shown. Conjugate addition of a cuprate reagent to the a,P-unsaturated epoxide (85) provides the liP-substituted steroid (86) stereospecificaHy (131). Subsequent steps lead to the synthesis of RU 486 (84). 

Mukaiyama reported tlie conjugate addition of a-ditliioalkylcuprates to 2-enones i73-9496 yields) for tlie syntliesis of 1,4-diketones, and tlie reaction was exploited in a syntliesis of t )-diliydtojasmone [ 141]. Few reports on a-tliioalkylcuprates have appeared since tlien. Cuprates formed from litliiated ketene ditliioacetals and... 

Conjugate additions lo a,/ -unsalutaled kelones and eslets ate die most Impotlanl ctiptale reactions. Kinetic studies by Ktauss and Sniidi on MezCuIi and a variety of ketones teveaied die following kinetic cliatacterislics lEq. 10.5), fitsl otdet bodi in cuprate dimer and in die etione [60]. 

However, the configuration of the major isomer obtained in the conjugate addition to methyl ( )-3-[(35,)-3-tot-butoxycarbonyl-2,2-dimcthyl-4-oxazolidinyl]-2-propenoate (entry 3) did not depend on the cuprate type alkyl-, vinyl-, 2-methylpropenyl-, phenyl-, and benzvl-cuprates induced the same sense of asymmetry, although the absolute configuration was not determined5. Here also, the stereochemical outcome was not dependent upon the geometry of the double bond. 

The conjugate addition of lithium cuprates to cinnamates 1 bearing a chiral oxazolidine or imidazolidine ring at the ortho position produced 2 in good to excellent yield upon hydrolysis14. 

The conjugate addition of medium-order cuprate reagents Li2Cu3Bu5 to 2-cyclohexen-l-one in the presence of 2 equivalents of (4S,5/ )-2-dimethylamino-3-isopropyl-4-methyl-5-... 

The conjugate addition to acyclic enones is summarized in Table 5. The chiral hetero-cuprate derived from (S)-prolinol or cinchonidine produced products of low enantiomeric excess on treatment with chalcone (entries 3 and 4), while the cuprate from (S)-yV-methylpro-linol gave 64% ee (entry 6). Under more dilute conditions, 88% cc was obtained (entry 5). (2[Pg.909]

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