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A is the kinetic, less-hindered-side silyl enol ether. Its double bond lies away from the methyl substituent. Forming B requires removal of a proton from the more hindered $\alpha$ position adjacent to the methyl-bearing carbon.

The base strengths alone do not determine the ratios. trimethylsilyl triflate is strongly electrophilic: oxygen silylation activates the ketone towards deprotonation, and irreversible trapping of the resulting silyl enol ether can make the product ratio reflect competing deprotonation rates. A weak amine therefore need not first produce a substantial equilibrium concentration of the free ketone enolate.

DBU is the strongest and comparatively accessible base, and distinguishes the two sites least strongly, giving the smallest A:B ratio. Triethylamine gives greater preference for the less-hindered site. The more sterically hindered diisopropylethylamine discriminates most strongly and gives the largest proportion of A. Its slightly higher conjugate-acid $p{K}_a$ than that of triethylamine does not reverse this trend, because steric accessibility and the coupled silylation/deprotonation mechanism matter alongside basicity. The data do not establish a simple thermodynamic enolate distribution.