(<i>Z</i>)<i>-</i>Trifluoromethyl-Trisubstituted Alkenes or Isoxazolines: Divergent Pathways from the Same Allene
作者:Chaolun Liu、Glenn P. A. Yap、Casey A. Rowland、Marcus A. Tius
DOI:10.1021/acs.orglett.0c02546
日期:2020.9.18
protonation of trifluoromethyl allenes leads to tri- or tetrasubstituted alkenes with high (Z)-selectivity. Treatment of the same allenes with catalytic Au(I) initiates a reaction cascade that produces isoxazolines in high yield.
observed in the reduction of hinderedketones such as isopropyl ketone, while the stereoselectivity was inverted in the reduction of ketones with electron-withdrawing atoms such as chlorine. The mechanism for the inversion in stereochemistry was investigated by enzymatic studies. Several enzymes with different stereoselectivities were isolated; one of them catalyzed the reduction of methyl ketones, and another
Reduction of trifluoromethyl ketones by a crude alcohol dehydrogenase from Geotrichum afford (S)-trifluoromethyl carbinols in excellent ee, whereas the reduction of methyl ketones gives the corresponding alcohols of the opposite configuration in excellent ee.
Difluoroenol silyl ethers 5 and 6, difluoroketene silyl (O,O-, O,S-, and O,N-) acetals 9 and 21, and 2,2-difluoro-2-trimethylsilylacetates 10 were prepared by electroreductive defluorination of trifluoromethyl ketones and trifluoroaceticacidderivatives in an MeCN-TBAB-chlorotrialkylsilane system using a carbon rod as an anode and a lead plate as a cathode. TBAF- or KF-CuI-promoted alpha-alkylation
α-fluorinated ketones with m-chloroperbenzoic acid (m-CPBA) under mild conditions. The yield of the esters was influenced by the choice of solvent, base, and substituent on the aryl group of the ketones. 4-Methoxyphenyl substituted fluoroketones were oxidized almost quantitatively with m-CPBA within 10 min to 12 h at room temperature using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a cosolvent with CH2Cl2
被有效地用α-氟化酮的拜尔-维利格氧化制备α-氟化酯米氯过苯甲酸(米温和条件下-CPBA)。酯的产率受酮的芳基上的溶剂,碱和取代基的选择影响。在室温下,使用1,1,1,3,3,3-六氟-2-丙醇(HFIP)与CH 2 Cl作为助溶剂,在10分钟至12小时内,用m -CPBA几乎定量地氧化了4-甲氧基苯基取代的氟代酮。2(1:1,v / v)和水性缓冲液(KH 2 PO 4-NaOH,pH 7.6)作为添加剂。α-氟代酮的氧化反应速率高于相应的非氟代酮的氧化反应速率。氟甲基芳基酮的α位上的氟原子增强了BAeyer-Villiger氧化反应的活性。