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NickelII-catalyzed asymmetric photoenolization/Mannich reaction of (2-alkylphenyl) ketones† † Electronic supplementary information (ESI) available: 1H, 13C{1H} and 19F{1H} NMR, HPLC spectra, and CD spectra. X-ray crystallographic data for C1, E1 and F1′. CCDC 2081680, 2130299 and 2171982. For ESI and crystallographic data in CIF or other electronic format see https://doi.org/10.1039/d2sc02721f

ABSTRACT: A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of ortho-alkyl aromatic ketones with benzosulfonimides was established by utilizing a chiral N,N′-dioxide/Ni(OTf)2 complex as the Lewis acid catalyst. It afforded a series of benzosulfonamides and the corresponding ring-closure products, and a reversal of diastereoselectivity was observed through epimerization of the benzosulfonamide products under continuous irradiation. On the basis of the control experiments, the role of the additive LiNTf2 in achieving high stereoselectivity was elucidated. This PEM reaction was proposed to undergo a direct nucleophilic addition mechanism rather than a hetero-Diels–Alder/ring-opening sequence. A possible transition state model with a photoenolization process was proposed to explain the origin of the high level of stereoinduction. A diastereo- and enantioselective photoenolization/Mannich (PEM) reaction of (2-alkylphenyl) ketones with benzosulfonimides is realized by a chiral N,N′-dioxide/NiII complex catalyst.

SUBMITTER: Yang L

PROVIDER: S-EPMC9337722 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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