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
Photoredox-Catalyzed Cascade Difluoroalkylation and Intramolecular Cyclization for Construction of Fluorinated γ-Butyrolactones
作者:Wanxing Sha、Wenzhong Zhang、Shengyang Ni、Haibo Mei、Jianlin Han、Yi Pan
DOI:10.1021/acs.joc.7b01279
日期:2017.9.15
difluoroalkylation and intramolecular cyclization reaction has been developed for the synthesis of difluoroalkylated oxygen heterocycles. The reaction was carried out under very mild conditions, affording fluorinated isobenzofuran-1-ones, lactone, and cyclic ethers with up to 97% chemical yields. Furthermore, several types of bromofluoroalkane precursors bearing ester, keto, amido, and phosphate groups could all work
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
A novel visible light mediated cyclization of enol lactones with difluoroacyl arenes via a free radical tandem difluoroalkylation and C–C coupling of butenolides is presented. This strategy provides a facile approach to potential biological fluorinated γ-butyrolactones with excellent diastereoselectivity.
Visible light-mediated metal-free alkyl Suzuki–Miyaura coupling of alkyl halides and alkenylboronic acids/esters: a green method for the synthesis of allyl difluoride derivatives
作者:Chuan-Hua Qu、Xiao Yan、Shu-Ting Li、Jian-Bo Liu、Zhi-Gang Xu、Zhong-Zhu Chen、Dian-Yong Tang、Huan-Xiang Liu、Gui-Ting Song
DOI:10.1039/d3gc00368j
日期:——
metal residues in this process are an unavoidable challenge. Herein, we report the first visible-light-driven photocatalyst-free coupling reaction of alkenylboronic acids/esters with α-bromodifluoroacylarenes, providing streamlining access to a series of Suzuki coupling products. The reactions proceed under metal-free conditions with a wide substrate scope. Mechanistic experiments and DFT calculation