Merged 1,2- and 1,3-asymmetric induction

The directed aldol reaction in the presence of TiC found many applications in natural product synthesis. Equation (7) shows an example of the aldol reaction utilized in the synthesis of tautomycin [46], in which many sensitive functional groups survived the reaction conditions. The production of the depicted single isomer after the titanium-mediated aldol reaction could be rationalized in terms of the chelation-controlled (anft-Felkin) reaction path [37]. A stereochemical model has been presented for merged 1,2- and 1,3-asymmetric induction in diastereoselective Mukaiyama aldol reaction and related processes [47]. 

In the Type II allylation reactions of a-methyl-/i-alkoxy aldehydes, the principles of 1,2- and 1,3-asymmetric induction both contribute to the reaetion diastereo-selectivity. Evans and co-workers have explained the stereoehemical outcome of these reactions in terms of a merged 1,2- and 1,3-asymmetric induction model [931- For example, the 2,3-anti aldehyde 135 reacts with allyl- and methallyltri-n-butylstannanes 98, generating the Felkin homoallylic alcohols 136 with >99 1 diastereoselectivity (Eq. (11.8)) [93]. 

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