Organocatalysts Effect on the Stereoselectivity of [2,3]‐Wittig Rearrangement

Abstract

The organocatalytic [2,3]‐Wittig rearrangement of allyloxyketones was investigated. Extensive screening of chiral amine organocatalysts showed that small pyrrolidine‐based catalysts or simple phenylethylamine with the primary amino group were the most effective ones. Interestingly, CF3‐derived pyrrolidine affords the rearrangement product with an opposite absolute configuration to the product obtained by using the corresponding non‐fluorinated proline derived catalysts. Mechanistic and computational investigations were also performed.

New Advances in the Synthetic Application of Enantiomeric 1-Phenylethylamine (α-PEA): Privileged Chiral Inducer and Auxiliary

“…In the last decade, three organocatalytic reactions of this type have been reported. Specifically, the intramolecular tandem Michael-Henry reaction [80], α-fluorination of ketones [81], and Wittig rearrangement of ketones [82] were effectively carried out with α-PEA as an organocatalyst.…”

“…and Wittig rearrangement of ketones [82] were effectively carried out with α-PEA as an organocatalyst.…”

“…The third case involves the organocatalytic effect of α-PEA in sigmatropic [2,3]-Wittig rearrangement of allyloxyketones described in 2019 by the Šebesta group. Catalytic studies were carried out on many substrates, and numerous products were obtained in good yields and high enantiomeric excesses (Scheme 58) [82]. The third case involves the organocatalytic effect of α-PEA in sigmatropic [2,3]-Wittig rearrangement of allyloxyketones described in 2019 by the Šebesta group.…”

“…The third case involves the organocatalytic effect of α-PEA in sigmatropic [2,3]-Wittig rearrangement of allyloxyketones described in 2019 by the Šebesta group. Catalytic studies were carried out on many substrates, and numerous products were obtained in good yields and high enantiomeric excesses (Scheme 58) [82].…”

Asymmetric Organocatalytic [2,3]‐Wittig Rearrangement of Cyclohexanone Derivatives

“…[12] In 2019, Šebesta et al described the rearrangement of aliphatic cinnamyloxyketones using aminocatalysis and moderate enantioselectivity was obtained (ee up to 60 %). [18] We recently described a Wittig rearrangement of cyclic ketones as a method for the formal asymmetric alkylation of αbranched ketones. [13] The rearrangement of cinnamyloxycyclopentanones was performed in the presence of a Cinchona amine derived catalyst and the rearranged products were obtained in very good results (dr up to 5.2 : 1; ee up to 95 %/ 18 %).…”