SN2′-substitution reaction via two different conformers 6A or 6B leading to the E- or the Z-product

August 13, 2024

• Title:       

  SN2′-substitution reaction via two different conformers 6A or 6B leading to the E- or the Z-product

• Image Source:

  Stereoselective anti-S_N2′-Substitutions of Secondary Alkylcopper-Zinc Reagents with Allylic Epoxides: Total Synthesis of (3S, 6R, 7S)-Zingiberenol

• Mark:

  Scheme 2

• Associated context:

  The observed E/Z ratios by using 6a or 6b as electrophiles are rationalized in Scheme 2. The anti-substitution via conformer 6A affords the E-product, whereas the substitution of conformer 6B results in the Z-product. Depending on the  1,3-allylic strain, one conformer is more favored. If the residue R2 of the allylic epoxide is bulky, such as the phenyl group of electrophile 6b, the substitution proceeds via conformer 6A due to steric reasons.