Synthesis of α-Halo-α,α-difluoromethyl Ketones by a Trifluoroacetate Release/Halogenation Protocol
摘要:
Three series of alpha-halo-alpha,alpha-difluoromethyl ketones are prepared from highly alpha-fluorinated gem-dials by exploiting the facile release of trifluoroacetate, followed by immediate trapping of the liberated alpha,alpha-difluoroenolate with an electrophilic chlorine, bromine, or iodine source. The products are typically isolated in good yields, even in the case of sensitive, alpha-iodo-alpha,alpha-difluoromethyl ketones. Also, we demonstrate that an alpha-iodo-alpha,alpha-difluoromethyl ketone will participate in a copper-promoted reaction to forge a new carbon-carbon bond.
A transition-metal-free protocol for the difluoroalkylation of imidazopyridines with bromodifluoroaryl ketones promoted by visible light irradiation is presented. This protocol is distinguished by simple, mild, and catalyst-free reaction conditions with a wide reaction scope, which is complementary to existing difluoroalkylation strategies by photoredox scenarios. Additionally, this protocol potentially
Copper-mediated radical cyclization of naphthalenyl iododifluoromethyl ketones with olefins was successfully developed to generate a series of unprecedented gem-difluorodihydrophenanthrenones, especially 2,2-difluoro-3,4-dihydrophenanthren-1(2H)-one derivatives. This strategy features the use of cheap copper powder and excellent regioselectivity and diastereoselectivity, thus providing a facile approach
electron‐catalyzed, photochemical tandem carbodifluoroalkylation/radical cyclization of enol ethers is disclosed. The reactions occur via addition of difluoroacyl radicals to methylene‐2‐oxazolines and subsequent intramolecular base‐promoted homolytic alkyl substitution (BHAS) of the intermediate oxyl‐alkyl radicals. Initiation of the radical chain reaction is best achieved with a commercially available and cheap
been achieved using a chiral proton-bridged bisphosphine oxide complex (POHOP) as a catalyst precursor. Concerted Lewis/Brønsted base catalysis with bisphosphine oxide enabled the electrophilic bromination of electron-deficient alkenes, affording synthetically useful bromodifluoromethyl-containing oxazolines with excellent enantioselectivity (up to 99%). Gram-scale synthesis was also demonstrated.
chemoselective cascade reaction strategy towards the synthesis of benzo[b]azepines was developed. The method is characterized by simple and mild conditions, low cost, and a wide range of substrates. This method enabled the facile and efficient synthesis of a series of 2,3,4,5-tetrahydro-1H-benzo[b]azepine analogues with an appended fluorinated side chain.
开发了一种新型镍催化化学选择性级联反应策略来合成苯并[ b ]氮杂卓类药物。该方法具有条件简单温和、成本低廉、底物范围广等特点。该方法能够轻松有效地合成一系列带有氟化侧链的 2,3,4,5-四氢-1H-苯并[ b ]氮杂卓类似物。