Conjugate additions of organometallics

House investigated the role of cuprous ions in the conjugate addition of organometallic reagents. He found that the catalytic effect can be explained by the intervention of a methyl copper derivative, which reacts rapidly with the carbon-carbon double bonds of the conjugated system. 

TABLE 6. Conjugate addition of organometallic reagents to vinyl sulfones55... 

Deprotonation of the vinylic proton is a serious side-reaction in the conjugate addition of organometallic reagents to y-siloxy-a, /J-unsaturated sulfones (89)63b. The use of the... 

Tomioka K, Nagaoka Y (1999) Conjugate addition of organometallic reagents. In Jacobsen EN, Pfaltz A, Yamamoto H (eds) Comprehensive asymmetric catalysis, vol 3. Springer, Berlin Heidelberg New York, chap 31.1... 

Another very important method for specific enolate generation is the conjugate addition of organometallic reagents to enones. This reaction, which not only generates a specific enolate, but also adds a carbon substituent, is discussed in Section 8.1.2.3. 

The conjugate addition of organometallic reagents R M to an electron-deficient alkene under, for instance, copper catalysis conditions results in a stabilized car-banion that, upon protonation, affords the chiral yS-substituted product (Scheme 7.1, path a). Quenching of the anionic intermediate with an electrophile creates a disubstituted product with two new stereocenters (Scheme 1, path b). With a pro-chiral electrophile, such as an aldehyde, three new stereocenters can be formed in a tandem 1,4-addition-aldol process (Scheme 1, path c). 

The conjugate addition of organometallic reagents to an electron-deficient carbon-carbon double bond is one of the most widely used synthetic methods to generate enolate. It is well known that Grignard reagents usually give a mixture of 1,2- and 1,4-addition... 

The conjugate addition of organometallic reagents to a./i-unsaturated compounds is one of the basic methods in our repertoire for the construction of carbon-carbon bonds. These addition reactions have been used as key steps in the synthesis of numerous biologically active compounds, and show a broad scope due to the large variety of donor and acceptor compounds that can be employed. It is evident that a tremendous effort has been devoted over the last three decades to develop asymmetric variants of this reaction. ... 

Conjugate addition of organometallic reagents to electron-deficient olefins constitutes one of the versatile methodologies for forming carbon-carbon bonds. Although... 

Enantlomerically pure B-suhstituted carbonyl compounds serve as useful intermediates in the synthesis of many chiral organic compounds. The enantloselective synthesis of acyclic 0-substituted carboxylic acids has been reported by Meyers, Mukaiyama, and Koga. However, no effective, general method for the enantio-controlled preparation of P-substituted cycloalkanones was available prior to the investigations by the submitters. For example, poor enantloselectivity was observed in conjugate additions of organometallic... 

The addition of organometallic reagents to push-pull alkenes is a synthetically important process in which retention of an alkenic unit in the product occurs this process complements the direct conjugate addition of organometallic reagents to activated alkynes (Section 1.2.5) which is complicated primarily... 

Suppl.to Chapter 31.1 Conjugate Addition of Organometallics to Activated Olefins... 

Reactions that result in the formation of C C bonds are of central importance in the construction of organic molecules. One such reaction is the conjugate addition of organometallic reagents to a,/3-unsaturated carbonyl... 

Diastereoselective Conjugate Addition of Organometallic Reagents to Chiral a,P-Unsaturated Amides and Imidazolidi-nones Derived from Ephedrine. Grignard reagents (2 equiv) add to chiral a,P-unsaturated amides derived from ephedrine in a 1,4-addition manner with high diastereoselectivities. Subsequent acidic hydrolysis affords optically active p-substituted carboxylic acids with 85-99% ee (eq 3). ... 

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