Conjugate organocatalyzed

The first organocatalyzed conjugate addition of a-substituted p-ketoester to a,P-unsaturated ketones was presented by Deng et al. [42] (Scheme 3). Although traditional Cinchona alkaloids were efficient catalysts for conjugate addition of carbon nucleophiles to nitroalkenes and sulfones, replacement of the C(9)-OH with an ester group (Q-7b) showed great improvement in stereoselectivity. The reaction is applicable to a variety of cyclic and acyclic enones (16,18). 

Enantioselective organocatalytic conjugate additions such as Michael and aldol reactions have been intensely studied under new catalysts. However, only a few organocatalyzed Michael reactions have been developed. The reaction involves construction of a new C-N bond that is very attractive for syntheses of molecules with biological properties. 

In contrast with metal-complex catalyzed transformations [52], enantioselective organocatalyzed intermolecular conjugate additions of O-nudeophiles seem to be limited to peroxides such as hydrogen peroxide or tert-butyl hydroperoxide. In these reactions the primary addition product, a / -peroxy enolate, reacts further to yield an epoxide (Scheme 4.31). Consequently, reactions of this type are covered in Section 10.2 Epoxidation of Enones and Enoates . 

Burstein C, Glorius F (2004) Organocatalyzed conjugate umpolung of a,fS-unsaturated aldehydes for the synthesis of y-butyrolactones. Angew Chem Int Ed 43 6205-6208... 

AsymmeUic organocatalyzed conjugate additions n Asymmetric organocatalyzed reactions... 

Some interesting organocatalyzed asymmetric double conjugate additions have been recently reported. For instance, the hydrochloride salt of chiral imidazolidinone... 

Scheme 2.9 Effect of olefin geometry on the organocatalyzed conjugate reduction of P-nitroacrylates...

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