Vinyl methyl ketone, complexes with group

A Pt pincer complex is able to be bonded to the optically active hyperbranched polyglycerol as pendant groups 594. The CD spectra of the polymer complex with different absolute configuration of the monomer units show opposite signs of the peak at 262 nm. The polymer-bonded complex catalyzes asymmetric addition of ethyl a-cyanoacetate to methyl vinyl ketone." " ... 

The second group of reactions is called vicinal difunctionalization. They embrace the C2 and C3 positions of the furan ring simultaneously. Thus, complex 3 (X = O, R = R = R = H) reacts with benzaldehyde dimethyl acetal to give 4H-furanium cation (the product of electrophile addition at C4), which experiences further attack by the methoxide group with formation of the acetal 8 (950M2861). This reaction is possible in the presence of the Lewis acid (BF3—OEt2). Reaction with methyl vinyl ketone in methanol, when run in identical conditions. 

In an important new application of crown ethers Cram and Sogah have recently reported that potassium bases complexed to chiral crown ethers catalyze the stereoselective Michael addition of a /3- ketoester to methyl vinyl ketone in high optical yields (81CC625). With chiral crown (46), carbanion (47) gave alkylated products with an optical yield of about 99% enantiomeric excess. These impressive results were rationalized by complex structure (48) in which the crown-complexed K+ and the carbanion form an ion pair. One face of the associated carbanion is shielded from electrophilic attack by the flanking binaphthyl groups and the approach of methyl vinyl ketone occurs in a stereoselective manner. 

Reaction of (trimethylsilyl)vinyl selenide 122 with methyl vinyl ketone catalyzed by SnCLt gives the [2 + 2] adduct 123 in 66% yield (equation 51)176. Replacement of the MegSi group with a hydrogen atom or a methyl group produces a complex mixture. Thus, the MesSi group can suppress side reactions by its steric effect. 

Reduction of 2,2-dimethyl-cyclohexane-1,3-dione (50) with Baker s yeast gave alcohol (ee 98.3%) whose tetrahydropyranyl derivative on methoxycarbonylation produced (51) quantitatively. Michael addition of (51) with methyl vinyl ketone followed by heating the adduct under reflux with pyrrolidine in benzene yielded (52) in 85% yield as stereoisomeric mixture whose separation presented problems. In order to eliminate the complexity due to a chiral center in tetrahydropyranyl protective group, deprotection of (52) was achieved by treatment with p-toluenesulphonic acid in methanol. The product obtained was a mixture of the lactone (53) and hydroxy ester (54). Probably the stereoisomer of... 

Due to the chelating effect of the amino group, allylic amines readily undergo nucleophilic addition reaction on their double bond. For example, carbopallada-tion of allyl-dimethylamine with malonates readily yields a chelating complex. Subsequent olefin insertion of methyl vinyl ketone into this complex gives co-amino enones23) (Scheme 17). An interesting application of the facile earbopalladation de-... 

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