BIMP‐Catalyzed 1,3‐Prototropic Shift for the Highly Enantioselective Synthesis of Conjugated Cyclohexenones

Abstract

A bifunctional iminophosphorane (BIMP)‐catalysed enantioselective synthesis of α,β‐unsaturated cyclohexenones through a facially selective 1,3‐prototropic shift of β,γ‐unsaturated prochiral isomers, under mild reaction conditions and in short reaction times, on a range of structurally diverse substrates, is reported. α,β‐Unsaturated cyclohexenone products primed for downstream derivatisation were obtained in high yields (up to 99 %) and consistently high enantioselectivity (up to 99 % ee). Computational studies into the reaction mechanism and origins of enantioselectivity, including multivariate linear regression of TS energy, were carried out and the obtained data were found to be in good agreement with experimental findings.

Bi-functional and mono-component organocatalysts for the ring-opening alternating co-polymerisation of anhydride and epoxide

“…However, the urea is not deprotonated by the iminophosphorane, which would result in a zwitterionic species. Such a zwitterionic species is energetically unfavoured 40 (with respect to the neutral monomer: ΔG = 9.0 kcal mol −1 ) and would significantly differ in its 31 P chemical shift (δ31 P = 36 ppm) from the neutral monomeric species. On the other hand, the dimerisation of the neutral monomeric species is energetically favoured (with respect to the neutral monomer: ΔG = −28.2 kcal mol −1 ) thanks to the formation of multiple hydrogen bonds (cf.…”