The carbocation structure after the nitrogen elimination, INT3, presents as a shoulder on the PES and the sequential process tends to be barrierless (ie ΔG ‡ (TS3) = 0 kcal mol -1 ). The group involved in the 1,2 shift or oxygen insertion must be at an anti-periplanar position relative to the leaving nitrogen. Hence, the stereochemistry of the product is determined by the stereochemistry of INT2 at C4 and C5. The chemoselectivity is controlled by the process after INT2. Thus, the focus of this investigation for understanding selectivity will be on the addition between aldehyde and INT1 via TS1 and nitrogen elimination via TS2.