Michael addition dienolate double

A double ir-face selective aptotic Michael addition of the lithium dienolate, derived from the chiral senecioate (119), to cyclopentenone served for the total synthesis of (-)-kushimone (120 Scheme 45).137-138 The selectivity of the key reaction was rationalized by the assumption of a transition state as shown in (121a). A related approach involves the Michael addition of enolates, derived from chiral propionates, to methyl ( )-crotonate (Scheme 46).139 The formation of the threo isomer (122) as the major product indicates a transition state structure as shown in (121b). This method was utilized in the synthesis of the marine natural product 7,20-diisocyanoadociane (123 Scheme 47).140... 

Sequential double Michael addition of cyclic dienolates, generated from (107) or (108), to fulvene (109) has been developed as a method for rapid access to the tricyclo[5.3.0. 2,5]alkane system (Scheme 24).90... 

In an asymmetric approach to the bicyclo[2.2.2]octane ring system, a double Michael addition has been employed using phenylmenthyl acrylate as the initial Michael acceptor. The condensation of the dienolate, generated with Lithium Diisopropylamide, reacts with the acrylate to afford the bicyclo[2.2.2]octane derivative (eq 6). The de for the reaction is only 50% however, it is highly endo selective (>95%). ... 

In efforts towards a synthesis of eremolactone, the dienolate (158) has been found to react with the cyano-ester (159) to give (160) (probable stereochemistry shown) most likely via a double Michael addition rather than a Diels-Alder reaction. Highly substituted cyclohexanes have been prepared by cycloadditions between cyclohexa-1,3-dienes and nitroso-compounds followed by N—O and olefinic bond cleavage (Scheme 12). ... 

Hong and coworkers [62] reported a sequential double-Michael addition of lithium dienolates 255 to pentafulvene 47 (Scheme 7.56). The reaction provides an efficient route to the tricyclo[5.3.0.w ]alkane ring systems 256. In addition, the reaction is attractive as two bonds and three stereocenters are formed in one step with high stereoselectivity. 

Scheme 1.20. Double Michael-type addition of dienolate 220 to Cgo, affording after workup the thermodynamically more stable Irans-disubstiluted ketone ( )-219. Due to steric congestion, the corresponding civ-adduct is not available through Diels-Alder reaction with the silyl enol ether corresponding to 220. Reduction of the racemic ketone ( )-219 with DIBAL-H diastereoselec-tively affords alcohol ( )-223.

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