Concerted versus ionic mechanisms of the α and γ extensions in uncatalyzed Mukaiyama reaction between β,γ-unsaturated bis silyl ketene acetal and benzaldehyde: A DFT study

The uncatalyzed regioselective Mukaiyama aldol reaction between β,γ-unsaturated bis silyl ketene acetal and benzaldehyde has been studied theoretically using density functional theory with the M06-2X exchange–correlation functional. These DFT calculations mostly demonstrate that (i) the α and γ adducts in uncatalyzed Mukaiyama reaction can proceed through two mechanisms, ionic and concerted, (ii) the concerted mechanism is favored for the α adduct and it is disfavored for the γ adduct, (iii) under 12 and 17 kbar, the α adduct reaction path is below the γ adduct reaction path whereas if the pressure decreases to 5 kbar, the opposite is obtained.