<scp>Monofluoromethyl‐Substituted</scp>
Sulfonium Ylides: Preparation,
<scp>Structure‐Reactivity</scp>
Study and Substrate Scope
<sup>†</sup>
作者:Xin Hong、Yafei Liu、Long Lu、Qilong Shen
DOI:10.1002/cjoc.202000206
日期:2020.11
Structure‐reactivity study of a family of electrophilic monofluoromethylating reagents based on sulfonium ylide skeleton with different steric hindrance and electron‐withdrawing properties was described. These studies led us to discover two highly reactive reagents 3 with a cyclic malonate backbone and 6 with an electron‐poor 1,1,1,5,5,5‐hexafluoropentane‐2,4‐dione backbone. The high reactivity of reagent
phase‐transfer catalyst (PTC) can mediate the highlyenantioselectivetrifluoromethylthiolation of β‐ketoesters with the previously developed SCF3 reagent (see scheme). Reactions of indanone‐derived β‐ketoesters occurred with high yield and excellent enantioselectivity with quinine as catalyst. Reactions of tetralone‐ or 1‐benzosuberone‐derived β‐ketoesters occurred with moderate to good enantioselectivity with
Using visible light as a driving force and molecular oxygen as a green oxidant, we developed bis(oxazoline)–Ni(acac)2 catalyzed asymmetric α-hydroxylation of β-keto esters under low photosensitizer loading, and the protocol enabled an efficient transformation to provide the desired chiral α-hydroxy-β-keto esters in high yields (up to 99%) and enantioselectivities (up to 99% ee) at room temperature
A series of bifunctional metal-free photo-organocatalysts have been developed by grafting the photosensitizer to cinchona-derived phase-transfer catalysts. Using air as a green oxidant and visible light as the driving force, these catalysts are applied to the oxidation of a range of β-dicarbonyl compounds in good yields (up to 97%) and enantioselectivities (up to 93:7 er).
An efficient and enantioselective photo-organocatalytic [small alpha]-hydroxylation of [small beta]- dicarbonyl compounds using molecular oxygen has been extended. This simple catalytic procedure is applicable to a range of [small beta]-keto esters and [small beta]-keto...