Asymmetric allylation of aldehydes, ketones, and acetals

Allylsilacycles bearing a chiral 1,2-diol, /3-aminoalcohol, or 1,2-diamine ligand have been utilized for enantioselective allylation of aldehydes. 102 102a,i03,i06,l06a menti0ned above, they react with aldehydes spontaneously. Among them, allylsilacycles 16 show the highest enantioselectivity (Equation (24)). 

Similarly, optically active allenyltrichlorosilanes can be prepared from 1,3-enynes and HSiCl3.109 The DMF-pro-moted propargylation of aldehydes with allenyltrichlorosilanes effects complete chirality transfer by a syn-Se process. 

Under catalysis by a Pd complex with homochiral phosphine ligand 19, silaboration of terminal allenes with homochiral silylborane 18 shows high enantioface-selectivity by double asymmetric induction (Equation (25)).lls The resultant /3-borylated allylsilanes can be used for asymmetric carbonyl allylation. 

Catalytic asymmetric allylation of aldehydes and ketones with allylsilanes can be achieved by using chiral Lewis acids, transition metal complexes, and Lewis bases. In recent years, much attention has been paid for the chiral Lewis base-catalyzed system using allyltrichlorosilanes. Advances in catalytic asymmetric carbonyl allylation have been described in detail in recent reviews.116,117,117a 

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