Electrophilic Fluorinating Reagent Mediated Synthesis of Fluorinated α-Keto Ethers, Benzil, and 6,6‘-Dialkoxy-2,2‘-bipyridines

Abstract

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.

Selective Conversion of 5‐Hydroxymethylfuraldehyde Using Cp*Ir Catalysts in Aqueous Formate Buffer Solution

“…Ethyl acetate (99.5 %), petroleum ether (60∼90 °C), methanol (99.5 %), dichloromethane (99.5 %), isopropanol (99.5 %), hydrochloric acid (37 %), silver sulfate (99.7 %), formic acid (98.0 %), sodium formate dihydrate (99.5 %), Na 2 HPO 4 ⋅12 H 2 O (99.0 %), and NaH 2 PO 4 ⋅2 H 2 O (99.0 %) were purchased from Sinopharm Chemical Reagent Co., Ltd. Reagent water was purchased from Wahaha. The autoclave was provided by Anhui Kemi Machinery Technology Co., Ltd. [Cp*IrCl 2 ] 2 , 4,4′‐dihydroxy‐2,2′‐bipyridine, 4,4′‐diamino‐2,2′‐bipyridine, 6,6′‐dihydroxyl‐2,2′‐bipyridine, and 6,6′‐dimethoxyl‐2,2′‐bipyridine were synthesized according to the previously reported procedures.…”

Base-Mediated Synthesesof New 6,6′-Di(polyfluoroalkoxy)-2,2′-Bipyridines with100% Regioselectivity

“…In the presence of a nucleophile, such as RO -, attack occurs at the N-fluorocarbocation with concomitant loss of HF to give the isolated 6,6¢-dialkoxybipyridines (Scheme 1). 6 A similar reaction does not occur with R f OH. However, upon addition of a base, the reaction with R f Oproceeds as with RO -.…”

“…In the past several years, electrophilic fluorinating reagents have been used extensively to introduce fluorine into a variety of organic substrates. [1][2][3][4][5] However, recently we reported 6 a new application of N,N-difluoro-2,2¢-bipyridinium bis(tetrafluoroborate) (MEC-31) (1) to synthesize 6,6¢-dialkoxy-2,2¢-bipyridines in very good isolated yields and with excellent regioselectivity as shown in Scheme 1. The syntheses of the polyfluoroalkoxy bipyridines from polyfluoroalcohols did not proceed under analogous conditions.…”

Bipyridine‐Modulated Palladium‐Catalyzed Oxidative Heck‐Type Reactions of Arylboronic Acids with Olefins

“…1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were recorded on a Bruker AVA-300 spectrometer with TMS as internal standard. All reagents were used directly as obtained commercially.…”

“…After ordinary workup and being evaporated by rotary evaporator, the residue was purified by column chromatography to give the required homo-coupled derivative (hexane/ethyl acetate). 6,6¢-Dimethoxy-2,2¢-bipyridine (1d) 13 White solid, mp = 117-118°C; 1 H NMR (300 MHz,…”