姐妹花内衣Communication
Electrocatalytic fluoroalkylation of olefins
D.Y.Mikhaylov a ,Y.H.Budnikova a,*,T.V.Gryaznova a ,D.V.Krivolapov a ,I.A.Litvinov a ,D.A.Vicic b ,O.G.Sinyashin a
a A.E.Arbuzov Institute of Organic and Physical Chemistry,Kazan Scientific Center of Russian Academy of Sciences,8,Arbuzov Str.,420088Kazan,Russian Federation b
Department of Chemistry,University of Hawaii,2545McCarthy Mall,Honolulu,HI 96822,USA
a r t i c l e i n f o Article history:
Received 28May 2009
Received in revid form 10August 2009Accepted 11August 2009
Available online 15August 2009Keywords:
Nickel complexes Electrosynthesis Fluoroalkylation Olefin
a b s t r a c t
An efficient nickel-catalyzed method devoted to the direct addition of perfluoroalkyl halides (I,Br)to a -methylstyrene is described.This procedure allows for synthesis of compounds resulting from addition-dimerization in good yields.
Ó2009Elvier B.V.All rights rerved.
1.Introduction
The conjugate addition of organometallic reagents to electron-deficient olefins is a powerful method for formation of new car-bon–carbon bonds,yielding Michael adducts which reprent uful synthons to further organic transformations [1].Moreover,such methodology can be expanded to include the addition of rad-ical substrates to a ,b -unsaturated compounds ,and in many cas the radical additions proceed enantiolectively [2].The most commonly ud methods to generate radicals for olefin addition chemistry involve the oxidation of trialkylboranes [2],oxidation of organozinc reagents [3],and the reduction of alkyl halides by low valent metal complexes [4].The last of the methods can be made catalytic in metal complex upon the introduction of a chem-ical reducing agent [4]or by electrochemical means [5,6].Some of the metals capable of generating orga
nic radicals for olefin addi-tion chemistry via electrocatalytic reduction are [Ni(tet a)]2+[5],CoBr 2(py)x [7,8],NiBr 2(py)x [9](tet a =5,5,7,12,12,14-hexa-methyl-1,4,-8,11-tetra-azacyclotetradecan;py =pyridine).
荣耀和华为的关系With a few exceptions [4,7],most of the substrates ud in rad-ical olefin addition chemistry are unfunctionalized,thereby limit-ing the scope of the methodology.In efforts to further expand the scope we t out to explore the possibility of using electro-chemical methods to add perfluoroalkyl radicals across double bonds to generate new functionalized fluorocarbons.This class of substrates was chon becau fluoroalkyl moieties are becoming
increasingly important in the medicinal,materials,and agricultural fields [10–12],yet their chemical synthes remain problematic.In fact,while there has been many advances in incorporating the sim-plest fluoroalkyl group (trifluoromethyl)stoichiometrically into or-ganic electrophiles [13–22],only two catalytic process have ever been reported [23,24].Moreover,most of the catalytic and stoichi-ometric process employ expensive sources of the fluoroalkyl group,limiting their u in a large-scale process.The goal of the work prented was to demonstrate the proof-in-principle that lective additions of inexpensive perfluoroalkyl synthons to ole-fins can occur electrocatalytically under mild conditions.2.Results and discussion
The electrochemical reduction of Ni(II)to Ni(0)complexes is a key stage in many electrocatalytic reactions involving a -organo-nickel complexes [25–28],so NiBr 2bpy (bpy =bipyridine)was tar-geted for u in coupling fluoroalkyl halides and olefins.We have discovered that the joint electrolysis of NiBr 2bpy and fluoroalkyl halides (R f X,X =I,Br)in dimethylformamide in the prence of a -methylstyrene in cathode compartment of electrolizer (potential kept at À1.2V vs.SCE to regenerate Ni(0))yields new organic prod-ucts in which the perfluoroalkyl group has added to the olefin sub-strate (Eq.(1)).The cour of the reaction was followed by combined gas chromatography mass-spectrometry.The reactions can be run at 10mol%nickel catalyst to afford product in moderate yields.Interestingly,the end-product is a dimer,bearing two per-fluoroalkyl and two olefin synthons,unlike all previously described cas of electrocatalytic additions to olefins [1,5,7–9,25].
0022-328X/$-e front matter Ó2009Elvier B.V.All rights rerved.doi:10.1016/j.jorganchem.2009.08.015施工劳务
*Corresponding author.Tel.:+79172931629;fax:+78432732253.E-mail address:**************.ru (Y.H.Budnikova).Journal of Organometallic Chemistry 694(2009)
3840–3843
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a te /j o r g a n c h e
m
N N
NiBr
2DMF
Ph
+
R f X =C 6F 13I or H(CF 2)6Br
R f
Ph
Ph
R f
ps做印章R f X ð1Þ
The structure of 2,3-dimethyl-2,3-diphenyl-1,4-bis(perflu-orohexyl)butane (1)and 2,3-dimethyl-2,3-diphenyl-1,4-bis(6-H-perfluorohexyl)butane (2)were confirmed by X-ray analysis (Fig.1).Both molecules are located on a special position at the cen-ter of symmetry in the asymmetric unit cell,affording two frag-ments bearing chiral centers.Due to coincidence of molecular centers with the centers of inversion,each molecule is the meso form.
Several possible reaction mechanisms must be considered,including traditional organometallic mechanisms involving oxida-tive addition and reductive elimination as well as traditional radi-cal chain mechanisms.We can,however,note veral important features of the addition reactions.First,no reaction occurs in the abnce of a nickel catalyst.Second,the u of NH 4ClO 4as a proton source does not result in monomer formation,inconsistent with a mechanism like that shown in Eq.(2),which has literature prece-dence [5,29–31].Finally,a control experiment demonstrates that reduction of R f X at the electrode in the abnce of nickel and the prence of olefin does not result in olefin addition products or R f dimerization according to gas chromatography.Further studies
are underway to unravel more mechanistic features of the unu-sual addition
reactions.
ð2Þ
3.Conclusion
The new method reported herein allows for the introduction of inexpensive perfluoroalkyl synthons with long R f chains to olefins.This work is the first time that dimer formation occurs under elec-trocatalytic conditions.Further investigations in this area will hopefully afford ways to control monomer/dimer formation as well as stereochemistry of the resulting addition products.4.Experimental 4.1.X-ray analysis
财务总结
Data were collected on a Bruker Smart Apex II CCD diffractom-eter using graphite monochromated Mo K a (0.71073Å)radiation.Details concerning data collection and refinement are given in Table 1.D
ata were corrected for absorption using SADABS [32]pro-gram.All non-hydrogen atoms were refined anisotropically.The hydrogen atoms were calculated and refined as riding atoms.Data collection images were indexed,integrates,and scaled using the APEX 2data reduction package [33].Structure solution and refine-ment SIR [34],SHELXL 97[35],WINGX [36]program.Pictures were gen-erated with
ORTEP3for Windows [37].In molecules 1and 2
Fig.1.Molecular structure of ,3-dimethyl-2,3-diphenyl-1,4-bis(perfluorohexyl)butane (1)and 2,3-dimethyl-2,3-diphenyl-1,4-bis(6-H-perfluorohexyl)butane (2).Disordered atoms were omitted for clarity,thermal ellipsoids drawn at 30%probability.
D.Y.Mikhaylov et al./Journal of Organometallic Chemistry 694(2009)3840–38433841
fluorine atoms offluoroalkyl substituents are disordered in crystals and were refined with occupancy0.598(0.402)for1and 0.537(0.463)for2,respectively.
4.2.General procedures
All reactions were carried out under dry argon atmosphere.All solvents employed were purified and dried prior to u.N,N-Dimethylformamide was purified by double fractionation distilla-tion over melting potash.Perfluoroiodohexane and6-H-perfluo-robromohexane were purchad from P&M Invest and ud without further purification.a-Methylstyrene was procured from Acros Organics.Tetrabutylammonium tetrafluoroborate was pur-chad from Aldrich and recrystallized from diethylether.NiBr2bpy were prepared according reported procedure[26].Preparative electrolys wer
e performed by means of the direct current source B5-49in thermostatically controlled cylindrical divided40ml elec-trolyr(a three-electrode cell).Platinum with surface areas of 20cm2was ud as a cathode.The working electrode potential was determined using reference electrode SCE.During electrolysis, the electrolyte was stirred with a magnetic stirrer.The saturated solution of Et4NBF4in DMA was ud as anolyte,and the anode compartment was parated by ceramic membrane.The1H NMR spectra were recorded on a Bruker MSL-400(400MHz).IR spectra of the compounds were recorded on a FTIR spectrometer‘‘Vector 22’’(Bruker)in the400–4000cmÀ1range.Solid samples were pre-pared as KBr pellets.Mass spectra were recorded in EI mode using ThermoQuest TRACE MS.
4.3.Preparative electrolys
4.3.1.Electrosynthesis of2,3-dimethyl-2,3-diphenyl-1,4-
bis(perfluorohexyl)butane
A solution for electrolysis was prepared by mixing0.317g
(0.85mmol)NiBr2bpy,7.54g(16mmol)perfluoroiodohexane and 1g(8.5mmol)a-methylstyrene in DMF(70ml).Electrolysis was carried out in an electrochemical cell with paration of anode and cath
ode compartments at ambient temperature under argon atmosphere at the potential of a working electrodeÀ1.2V.The amounts of electricity pasd through the electrolyte were2F per one mole of perfluoroiodohexane(454mA h).After completing the electrolysis,the solution was washed with distilled water (100ml)and extracted with benzene(3ÁÂ100ml).The organic layer was dried over magnesium sulfate andfiltered.The residual solution was concentrated under reduced pressure and left over-night,then the white solid precipitated from the mixture,filtered and dried in vacuo to give2,3-dimethyl-2,3-diphenyl-1,4-bis(per-fluorohexyl)butane.Yield2.6g(70%).m.p.:160–162°C.1H NMR (400Hz,C6D6):d=1.45and1.46(two s,6H,CH3),2.25and3.23 (m,4H,CH2),7.07–7.19(m,10H,C6H5).IR(KBr,m,cmÀ1):1144, 1208,1237(C–F),1602(C@C aromatic),3069(HC@).EIMS,m/z (rel.intensity):437.0(1/2M+).Anal.Calc.:C,41.19;H,2.29;F, 56.52.Found:C,41.28;H,2.45%.
4.3.2.Electrosynthesis of2,3-dimethyl-2,3-diphenyl-1,4-bis(6-H-
perfluorohexyl)butane
A solution for electrolysis was prepared by mixing0.576g
(1.5mmol)NiBr2bpy,5.86g(15mmol)6-H-perfluorobromohex-ane and1.81g(15mmol)a-methylstyrene i
n DMF(100ml).Elec-trolysis was carried out in an electrochemical cell with paration of anode and cathode compartments at ambient temperature un-der argon atmosphere at the potential of a working electrode À1.2V.The amounts of electricity pasd through the electrolyte were2F per one mole of6-H-perfluorobromohexane(824mA h). After completing the electrolysis,the solution was washed with distilled water(150ml)and extracted with benzene(3Â100ml). The organic layer was dried over magnesium sulfate andfiltered. The residual solution was concentrated under reduced pressure and left overnight,then the white solid precipitated from the mix-ture,filtered and dried in vacuo to give2,3-dimethyl-2,3-diphenyl-1,4-bis(6-H-perfluorohexyl)butane.Yield 3.2g(49.6%).1H NMR (400Hz,C6D6):d=1.34and1.35(two s,6H,CH3),2.17and3.13 (m,4H,CH2),4.94(tt,2H,2J HF51.62Hz,3J HF5.12Hz),6.96–7.07 (m,10H,C6H5).IR(KBr,m,cmÀ1):1145,1208,1238(C–F),1600 (C@C),3071(HC@).EIMS,m/z:419.0(1/2M+).Anal.Calc.:C, 42.96;H,2.62;F,54.41.Found:C,42.58;H,2.51%. Acknowledgement
This work was supported by the RFBR grant N07-03–00213.
Table1
Crystallographic data for1and2.
Compound12
Empirical formula C30H20F26C30H22F24
Formula weight874.46838.48
Crystal color/habitus Colorless/prism Colorless/prism
cad比例怎么调Unit cell dimensions
a(Å)14.9307(16)14.984(7)
b(Å)11.1647(12)11.052(6)
c(Å)10.3937(11)10.416(5)
b(°)103.548(1)103.958(7)
V(nm3)1684.4(3)1674(1)
人本原理三个原则Density(calcd)(Mg mÀ3) 1.724 1.663
Absorption coefficient(mmÀ1)0.2010.191
F(000)868836
h Range for data collection(°) 2.30–26.0 2.32–26.0
Index rangesÀ186h617,À136k613,À126l612À186h618,À136k613,À126l612 Reflections collected1244712397
Independent reflections3302[R int=0.0217]3277[R int=0.0356]
Restraints/parameters109/37368/349
Goodness offit(GOF)on F2 1.241 1.028
Final R indices[I>2r(I)]R1=0.0775,wR2=0.2128R1=0.0724,wR2=0.1991
R indices(all data)R1=0.1033,wR2=0.2353R1=0.1335,wR2=0.2485
Largest difference in peak/hole(eÅÀ3)0.588/À0.3860.400/À0.296
Temperature293K,wavelength k0.71073pm,crystal system monoclinic,space group P21/c;crystal size(mm).Compound1.0.30Â0.20Â0.20.Compound2.
0.10Â0.10Â0.10;Z2(molecule in special position).
3842 D.Y.Mikhaylov et al./Journal of Organometallic Chemistry694(2009)3840–3843
Appendix A.Supplementary material
CCDC720933and720934contain the supplementary crystallo-graphic data for this paper.The data can be obtained free of charge from The Cambridge Crystallographic Data Centre dc.cam.ac.uk/data_request/cif.Supplementary data associ-ated with this article can be found,in the online version,at doi:10.1016/j.jorganchem.2009.08.015.
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