New fluorine-containing building blocks from trifluoroethanol. 2.
摘要:
A new fluorine containing acyl anion equivalent 1,1 -difluoro-2-lithio-2-[(N,N-diethylcarbamato)-ethene 9 has been prepared and trapped with a number of electrophiles in good yields. Transacylation of the first formed lithium alkoxides releases a difluoroenolate, affording difluoromethylketones upon work-up.
The generation of difluoroenolates from trifluoroethanol and reproducible syntheses of α,α-difluoro-β-hydroxy ketones
作者:Andrew S. Balnaves、Thomas Gelbrich、Michael B. Hursthouse、Mark E. Light、Michael J. Palmer、Jonathan M. Percy
DOI:10.1039/a902966d
日期:——
Metallated difluoroenol carbamate 1 reacted with aldehydes and ketones in the presence of highly oxophilic Lewis acid boron trifluorideâethyl ether; the Lewis acid attenuated the transacylation reaction to the corresponding enolates so that allylic alcohols could be isolated. Treatment of the allylic alcohols with strong base afforded difluoroenolates which could be trapped cleanly in aldol reactions.
Developing the Saegusa–Ito Cyclisation for the Synthesis of Difluorinated Cyclohexenones
作者:Jonathan M. Percy、Adam W. McCarter、Alan L. Sewell、Nikki Sloan、Alan R. Kennedy、David J. Hirst
DOI:10.1002/chem.201503653
日期:2015.12.21
the turnover of the initial palladium(II) salt, whereas the provision of an oxygen atmosphere ensured more rapid reaction. Annulations required a minimum level of substitution on the chain, but failed when the alkene was substituted. Annelations allowed a range of n,6‐bicyclic systems to be prepared and afforded three products, in which heterocycles were fused to the new cyclohexenone. The least substituted
Towards novel difluorinated sugar mimetics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones
作者:Gerry A. Griffith、Jonathan M. Percy、Stéphane Pintat、Clive A. Smith、Neil Spencer、Emi Uneyama
DOI:10.1039/b505978j
日期:——
Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT (19)F NMR. Topological characterisation by molecular modelling and NOESY/ROESY
Modular Construction of Fluoroarenes from a New Difluorinated Building Block by Cross-Coupling/Electrocyclisation/Dehydrofluorination Reactions
作者:Jonathan M. Percy、Helena Emerson、James W. B. Fyfe、Alan R. Kennedy、Sergej Maciuk、David Orr、Lucie Rathouská、Joanna M. Redmond、Peter G. Wilson
DOI:10.1002/chem.201601584
日期:2016.8.16
were used to assemble precursors to 6π‐electrocyclisations of three different types. Electrocyclisations took place at temperatures between 90 and 240 °C, depending on the central component of the π‐system; nonaromatic trienes were most reactive, but even systems that required the temporary dearomatisation of two arenyl subunits underwent electrocyclisation, albeit at elevated temperatures. Photochemical
One-pot near-ambient temperature syntheses of aryl(difluoroenol) derivatives from trifluoroethanol
作者:Sara H. Kyne、Jonathan M. Percy、Robert D. C. Pullin、Joanna M. Redmond、Peter G. Wilson
DOI:10.1039/c1ob06372c
日期:——
Difluoroalkenylzinc reagents prepared from 1-(2′-methoxy-ethoxymethoxy)-2,2,2-trifluoroethane and 1-(N,N-diethylcarbamoyloxy)-2,2,2-trifluoroethane at ice bath temperatures underwent Negishi coupling with a range of aryl halides in a convenient one pot procedure. While significant differences between the enol acetal and carbamate reagents were revealed, the Negishi protocol compared very favourably with alternative coupling procedures in terms of overall yields from trifluoroethanol.