Aldol additions single asymmetric induction

In order to understand the phenomenon of double asymmetric induction, we need to have a clear picture of the inherent selectivities of each of the chiral partners in closely related single asymmetric induction processes. Consider for example the kinetically controlled aldol addition reactions shown in Scheme 1.5... 

Scheme 1.5. Examples of single and double asymmetric induction in the aldol addition reaction, (a) Reaction of a chiral enolate and an achiral aldehyde (b) Reaction of an achiral enolate with a chiral aldehyde (c) Matched pair double asymmetric induction with a chiral enolate and a chiral aldehyde (d) Mismatched pair double asymmetric induction with a chiral enolate and the aldehyde enantiomeric to that shown in (a). (After ref. [58]).

This retro aldol protocol enabled an ideal catalytic kinetic resolution of racemic aldol adducts that are usually difficult to be obtained through forward processes as illustrated by the resolutions of cyclohexanone aldol adducts. An intriguing feature of this process is that one chiral primary amine (e.g. 29) could catalyze stereoselectively the resolution of both anti- and yn-configured aldol adducts, whereas the forward reactions with the same catalyst yield selectively anti-configured aldol products. In addition, the catalytic power of 29-TfOH on both aldol and retro aldol reactions has also made possible an unprecedented asymmetric transfer aldol reaction that can generate two enantioenriched aldol adducts with opposite chiral induction from a single chiral catalyst (e.g. aldol products 48 and 49 in Scheme 5.14) [27],... 

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