3-Trimethylsilyl-3-butene-2-one

In contrast, the diastereoselectivity of the conjugate addition of a chiral alkenylcoppcr-phosphinc complex to 2-mcthyl-2-cyclopentenone was dictated by the chirality of the reagent63. The double Michael addition using the cyclopentenone and 3-(trimethylsilyl)-3-buten-2-one and subsequent aldol condensation gave 4 in 58 % overall yield. The first Michael addition took place from the less hindered face of the m-vinylcopper, in which chelation between copper and the oxygen atom fixed the conformation of the reagent. 

D. 3-Trimethylsilyl-3-buten-2-one (4). A solution of 55 g. of crude butenol 3 in 100 ml. of acetone is placed in a 500-ml., three-necked, round-bottomed flask equipped with a mechanical stirrer and a 250-ml. dropping funnel. The reaction vessel is immersed in an ice-water bath, and 95 ml. of an aqueous solution containing chromic acid and sulfuric acid (Note 13) is added to the stirred acetone solution. After completion of the addition, isopropyl alcohol is added to the reaction mixture until a green endpoint is reached, indicating consumption of the excess oxidant. The contents are poured into 450 ml. of ethyl ether, 300 ml. of water are added, and the aqueous layer is saturated with sodium chloride. The layers are separated, and the aqueous solution is extracted with five 150-ml. portions of ethyl ether. The combined ether solutions are washed with two 150-ml. portions of saturated aqueous sodium... 

Trimethylsilyl-3-buten-2-ol, 58, 153, 157 3 TRIMETHYLSILYL-3-BUTEN-2 ONE, MICHAEL ACCEPTOR FOR CONJUGATE ADD1TION-ANNELATION, 58, 158... 

As shown in Scheme 20, manipulation of (-)-isopulegol as described previously108 provided smooth access to the Robinson precursor hydroboration of (-)-isopulegol with oxidative workup followed by selective protection provided alcohol 246, followed by Swern oxidation to give 247.49 Generation of the kinetic enolate of 247 with LDA at low temperature followed by Michael addition to 3-trimethylsilyl-3-buten-2-one gave, after mild in situ hydrolysis of the a-silyl... 

TRIMETHYLSILYL-3-BUTEN-2-ONE AS MICHAEL ACCEPTOR FOR CONJUGATE ADDITION-ANNELATION cis -4,4a,5,6,7,8-HEXAHYDRO-4o,5-DIMETHYL-2(3H)-NAPHTHALENONE... 

Trimethylsilyl-3-buten-2-one as Michael Acceptor for Conjugate ADDmON-ANNELATION cis-4,4a,5,6,7,8-HEXAHYDRO-4a,5-DIf4ETHYL-2(3H)-... 

Annulation. 3-Trimethylsilyl-3-buten-2-one has been employed as a methyl vinyl ketone homolog in an improved method for the annulation of ketones. Based on work by Stork and Ganem, who employed 3-triethylsilyl-3-buten-2-one as a Michael acceptor in the Robinson annulation reaction, Suzuki and co-workers prepared a functionalized bicyclic ketone via a silyl enol ether as shown in eq 1. In general, the annulation of 2-alkylcycloketones with methyl vinyl ketone and its homologs produces rather poor yields of the desired cyclized products. 

The conjugate addition of enolate anions to activated 3-trimethylsilyl-3-buten-2-one helped solve another long-standing problem in organic synthesis by permitting the annulation reaction to be carried out in aprotic solvents under conditions where enolate equilibration is avoided. The annulation of thermodynamically unstable lithium enolates with MVK, where equilibration to the more stable enolate occurs prior to Michael addition, often yields a mixture of stractmal isomers. For exan le, Boeckman successfully employed 3-trimethylsilyl-3-buten-2-one in a Robinson annulation sequence (eq 2). Thus treatment of cyclohexenone with lithium dimethylcuprate in diethyl ether and then with 3-trimethylsilyl-3-buten-2-one gives the desired Michael adduct, which is converted into the functionalized octalone in 52% overall yield. ... 

Michael Condensation. In 1988, Hagiwara and co-workers extended this annulation technology to include the two-fold Michael reaction of kinetic enolates derived from 1-acetylcyclohexenes (eq 4). The kinetic enolates of 1-acetylcyclohexenes are generated from the corresponding trimethylsilyl enol ethers by treatment with MeLi in THF prior to the addition of 3-trimethylsilyl-3-buten-2-one. This one-pot annulation produces the desired decalone as a single isomer in 39% yield. 

Michael-Peterson Condensation. 3-Trimethylsilyl-3-buten-2-one also undergoes smooth Michael addition with Grignard reagents (R = Me, n-Pr, i-Pr, f-Bu, Ph), generating magnesium enolates which are then trapped with benzaldehyde to give ( )-and (Z)-enone isomers after Peterson condensation (eq 6). For example, treatment of the a-silyl vinyl ketone with methylmagne-sium iodide followed by reaction with benzaldehyde yields a 7 1... 

Diene Adduct. 3-Trimethylsilyl-3-buten-2-one undergoes a Shapiro reaction to give the 2,3-bis(trimethylsilyl)buta-1,3-diene in 32% yield (eq 7). This compound undergoes Diels-Alder reactions with a number of dienophiles (e.g. maleic anhydride, ben-zoquinone) in benzene at 60 °C to give sUylated cycloaddition adducts. ... 

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