Organometallic addition to carbonyl

In the case of TGT structures which are acyclic or which contain isolated rings, the disconnection of non-ring bonds must be examined to identify those disconnections which may be most effective on topological grounds. However, for such acyclic disconnections the topological factors may be overshadowed by other structural considerations. For instance, if a powerful stereosimplifying disconnective transform, such as stereospecific organometallic addition to carbonyl... 

Something to bear in mind with all organometallic additions to carbonyl compounds is that the addition takes the oxidation level down one. in other words, if you start with an aldehyde, you end up with an alcohol. More specifically,... 

Let us work retrosyntheticaUy. Ether disconnection by retro-Williamson synthesis (Section 9-6) gives the tertiary alcohol D. How do we um vel D to CT Answer We go back to Section 8-9, recognizing that complex alcohols can be made fiom simpler ones by organometallic additions to carbonyl compounds ... 

There is another possible mechanism for addition of organometallic reagents to carbonyl compounds. This involves a discrete electron-transfer step. °... 

As well as the addition of achiral organometallic reagents to chiral aldehydes (see also Sections 1.3.2. and 1.3.3.), the addition of chiral organometallic reagents to carbonyl compounds is a well-known and intensively studied process which may lead to enantiomerically and/or diastereomerically enriched products. Chiral organometallic reagents can be classified into three groups ... 

Formation of C —C Bonds by Addition of Benzyl-Type Organometallic Compounds to Carbonyl Groups... 

Formation of C-C Bonds by Addition of Allyl-Type Organometallic Compounds to Carbonyl Compounds... 

For reviews of the addition of organometallic compounds to carbonyl groups, see Eicher, T. in Patai, Ref. 2, p. 621 Kharasch, M.S. Reinmuth, O. Grignard Reactions of Nonmetallic Substances, Prentice-Hall Englewood Cliffs, NJ, 1954, p. 138. For a review of reagents that extend carbon chains by three carbons, with some functionality at the new terminus, see Stowell, J.C. Chem. Rev., 1984, 84, 409. 

The stereoselectivity of reduction of carbonyl groups is effected by the same combination of steric and stereoelectronic factors which control the addition of other nucleophiles, such as enolates and organometallic reagents to carbonyl groups. A general discussion of these factors on addition of hydride is given in Section 3.10 of Part A. 

Organometallic reagents are better known for their involvement in the alkylations at ring nitrogen atoms in many heterocycles. However, under proper circumstances, they can promote addition to carbonyl groups. Such is the case when 68 is allowed to react with an excess of Me2BuMgLi at 0°C. The secondary alcohol 69 is obtained in fair yield (Equation 28) <20040L1991>. 

Enantioselective Addition of Organometallic Reagents to Carbonyl Compounds Chirality Transfer, Multiplication, and Amplification 255... 

ENANTIOSELECTIVE ADDITION OF ORGANOMETALLIC REAGENTS TO CARBONYL COMPOUNDS CHIRALITY... 

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