共老我白发Tetrahedron report number 743
Non-conventional methodologies for transition-metal catalysed
carbon–carbon coupling:a critical overview.
Part 1:The Heck reaction
Francisco Alonso,a,*Irina P.Beletskaya b,*and Miguel Yus a,*
a Departamento de Qu?
′mica Orga ′nica,Facultad de Ciencias and Instituto de S?′ntesis Orga ′nica (ISO),Universidad de Alicante,Apdo.99,E-03080Alicante,Spain
b Department of Chemistry,Lomonosov Moscow State University,Vorob’evy Gory,119992Moscow,Russia
Received 10August 2005
Available online 29September 2005
Contents
1.General introduction ..........................................................
117721.1.Substrates..............................................................
117731.2.Catalytic systems ........................................................
117731.3.Solvents ...............................................................
117741.3.1.Supercritical ?uids (SCFs)...........................................
117741.3.2.Ionic liquids (ILs)..................................................
117741.3.3.Fluorous media ...................................................
117751.3.4.Aqueous solvents ..................................................
117751.4.Reaction conditions ......................................................
117751.4.1.Physical activation .................................................
117761.4.1.1.Microwave ...............................................
117761.4.1.2.Ultrasound ................................................
117761.4.1.3.High pressure .............................................
117761.4.2.Physicochemical activation (11776)
0040–4020/$-see front matter q 2005Elsevier Ltd.All rights reserved.
doi:10.1016/j.tet.2005.08.054Tetrahedron 61(2005)11771–11835
Keywords :Heck reaction;Supercritical ?uids;Ionic liquids;Fluorous media;Aqueous solvents;Microwave;Ultrasound;High pressure;Nano?ltration;Microreactors;Ball-milling conditions.
Abbreviations :A,ampere;AAEMA,deprotonated form of 2-(acetoacetoxy)ethyl methacrylate;acac,acetylacetonate;Ad,adamantyl;A336,tricaprylmethylammonium chloride;atm,atmosphere;bbim,1,3-di-n -butylimidazolium;b ,block copolymer;bmim,1-butyl-3-methylimidazolium;BINAP,2,20-bis(diphenylphosphino)-1,10-binaphthyl;Boc,tert -butoxycarbonyl;BTF,benzotri?uoride (a ,a ,a -tri?uorotoluene);Cbz,benzyloxycarbonyl;co ,copolymer;COD,1,5-cyclooctadiene;Cy,cyclohexyl;DAB,1,4-diaminobutane;dba,dibenzylideneacetone;DBU,1,8-diazabicyclo[5.4.0]undec-7-ene;DEA,N ,N -diethylacetamide;DEC,dendrimer-encapsulated catalyst;dendr,dendrimer;DIPEA,diisopropylethylamine;DMA,N ,N -dimethylacetamide;DMF,dimethylformamide;DMG,N ,N -dimethylglycine;dppp,1,3-diphenylphosphinopropane;EDG,electron-donating group;EWG,electron-withdrawing group;Fc,ferrocenyl;F-dppp,?uorous-tagged 1,3-bis(diphenylphosphino)propane;HDAPS,N -hexadecyl-N ,N -dimethyl-3-ammonio-2-propanesulfonate;Hex,hexyl;IL,ionic liquid;LDH,layered double hydroxide;M,metal;MCM-41,hexagonally packed mesoporous molecular sieves;MW,microwave;Nf,nona?ate (nona?uoro-n -butane-1-sulfonyl);NMP,N -methylpyrrolidinone;P c ,critical pressure;PAMAM,poly(amidoamine);PEG,poly(ethylene glycol);pmim,1-n -pentyl-3-methylimidazolium;PNIPAM,poly(N -isopropylacrylamide);PNP,p -nitrophenyl;PS,polystyrene;Py,pyridyl;RCM,ring-closing metathesis;ROMP,ring-opening metathesis polymerisation;rt,room temperature;SAPO,silico aluminophosphate;sc,supercritical;SCF,supercritical ?uid;SCM,shell cross-linked micelles;SDS,sodium dodecyl sulfate;TBAA,tetra-n -butyl ammonium acetate;TBAB,tetra-n -butyl ammonium bromide;TBAC,tetra-n -butyl ammonium chloride;TBAF,tetra-n -butyl ammonium ?uoride;TEAC,tetraethylammonium chloride;Tf,tri?uoromethanesulfonyl;TPPDS,bis(p -sulfonatophenyl)phenylphosphane dipotassium salt;Na-TPPMS,mono(m -sulfonatophenyl)diphenylphosphane monosodium salt;m -TPPTC,tris(m -carboxyphenyl)phosphane trilithium salt;TPPTS,tris(m -sulfonatophenyl)phosphane trisodium salt;TXPTS,tris(4,6-dimethyl-3-sulfonatophenyl)phosphane trisodium salt;T c ,critical temperature;THF,tetrahydrofuran;THP,tetrahydropyranyl;TFA,tri?uoroacetic acid;Tol,tolyl;TOF,turnover frequency (mol of product per mol of catalyst h K 1);TON,turnover number (mol of product per mol of catalyst);Ts,p -toluenesulfonyl;ttmpp,tris-(2,4,5-trimethoxyphenyl)phosphane;wt,weight;XAFS,X-ray absorption ?ne structure.*Corresponding authors.Tel./fax:C 34965903549;(F.A.;M.Y.);fax:C 7959381844;(I.P.B.);
e-mail addresses:falonso@ua.es;beletska@org.chem.msu.ru;yus@ua.es
1.4.2.1.Micellar solutions (11776)
1.4.2.2.Microemulsions (11777)
1.4.3.Electrochemical activation (11777)
1.5.Miscellaneous non-conventional techniques (11777)
1.5.1.Nano?ltration (11777)
1.5.2.Microreactors (11777)
1.5.3.Ball-milling conditions (11778)
2.Objectives and organisation (11778)
3.Introduction to the Heck reaction (11778)
4.Substrates (11778)
4.1.Alternative arylating agents (11778)
4.2.Supported substrates (11782)
5.Catalytic systems (11785)
5.1.Ligands:ligand-free catalytic systems (11785)
5.2.Catalysts:supported catalysts (11787)
5.2.1.Carbon (11787)
5.2.2.Metal oxides and other inorganic materials (11788)
5.2.3.Clays,zeolites and molecular sieves (11795)
5.2.4.Polymers (11798)
5.2.5.Dendrimeric systems (11803)
6.Solvents (11806)
6.1.Supercritical?uids (11806)
6.2.Ionic liquids (11808)
6.3.Fluorous media (11814)
6.4.Aqueous solvents (11817)
7.Reaction conditions (11820)
7.1.Physical activation (11820)
7.1.1.Microwave (11820)
7.1.2.Ultrasound (11822)
7.1.3.High pressure (11822)
7.2.Physicochemical activation (11823)
7.2.1.Micellar solutions (11823)
7.2.2.Electrochemical activation (11824)
8.Miscellaneous non-conventional techniques (11824)
8.1.Nano?ltration (11824)
8.2.Microreactors (11825)
8.3.Ball-milling conditions (11826)
9.General conclusions (11826)
References and notes (11826)
Biographical sketches (11835)
1.General introduction
The formation of carbon–carbon bonds is a fundamental reaction in organic synthesis the ef?ciency of which has interested organic chemists for a long time ago.Aryl–aryl bond formation has been known for more than a century and was one of the?rst reactions involving a transition metal.1 Modern synthetic chemistry is also sustained by the use of transition-metal catalysts as powerful tools for carbon–carbon bond-forming processes.2Among these, carbon–carbon coupling reactions through the activation of carbon–hydrogen bonds,3as well as addition reactions,4 have experienced an increasing interest in the preparation of molecules,the access to which is not so straightforward using other methodologies.On the other hand,the transition-metal catalysed carbon–carbon bond formation developed in the1970s represented a milestone in synthetic organic chemistry that allowed the cross coupling of substrates in ways that would have previously been thought impossible.5This protocol has been substantially improved and expanded over the past30years,providing an indispensable and simple methodology for preparative organic chemists(Scheme1
).
Scheme1.
F.Alonso et al./Tetrahedron61(2005)11771–11835 11772
In spite of the fact that it would seem that most of the research on developing carbon–carbon coupling strategies has been done,some new challenges on this topic have emerged in the narrow boundary between the20th and21st century.A new mentality of the organic chemist is focussed on the design of new tendencies and methodologies able to make the already known chemical transformations simpler, faster,cheaper,greener and in general,more ef?cient processes.In particular,increasing attention has been paid to the‘green chemistry’of these processes,this concept being understood as the set of principles6that reduce or eliminate the use or generation of hazardous substances.7 The idea of atom-economical reactions may be also a useful concept in helping to promote thinking in the direction of sustainable chemistry.8In order to achieve all the goals mentioned above,several valuable and distinctive tech-niques,9which do not?nd daily use in the laboratory,can be applied by the organic chemist to operate at different levels including(a)the type of substrates,(b)the catalyst,(c)the solvent,(d)the reaction conditions,(e)the separation techniques and(d)the reaction vessel.An introductory commentary to remark the importance of any of these parameters follows.
1.1.Substrates
The majority of studies of metal-catalysed cross-coupling reactions involve a halide or sulfonate as the electrophile and an organometallic reagent as the nucleophile in which the carbon atoms to be coupled are all sp2-hybridized.There is,however,a substantial need for the development of successful cross-coupling reactions involving either alkyl halides or 5a98184be45c3b3567ec8bfcanic halides also take part in Heck-type reactions.On the other hand,all these processes have in common some lack of atom economy,8since the corresponding inorganic salts are obtained and require proper isolation and treatment.
In the past decade,there have been developments in palladium-catalysed coupling systems for Heck,Suzuki, Stille and Sonogashira reactions among others,as a consequence of the great interest in the development of coupling partners that are both more economical and readily accessible.In spite of the fact that organoboranes and organostannanes have been the reagents of choice for some of these reactions,there are still some drawbacks in their use:certain organostannanes such as the trimethyltins, Me3SnX and their by-products are toxic,whereas organo-boranes have a lack of stability,particularly alkyl-and alkynylboranes.
Consequently,the search for novel substrates for the cross-coupling reactions has been the focus of much attention,for example,carboxylic acids,anhydrides and esters,as well as sulfonium salts,thiol esters and thioethers,have emerged as interesting alternatives to aryl halides.10In particular, carboxylic acids do not generate large amounts of waste and they work in the absence of phosphane ligands.There is, however,no general advantage in terms of atom economy and their generation in not always readily accessible, producing stoichiometric amounts of salts as by-products. The Stille,Suzuki and Kumada reactions with alkyl and aryl ?uorides is a recent and promising research area leading to the cross-coupled products under generally mild reaction conditions.11The stability of vinylic tellurides has also been used in palladium-catalysed cross-coupling reactions for the preparation of stereochemically de?ned enynes and enediynes.The fact that these reagents work in the presence of sensitive functional groups and under mild reaction conditions makes them interesting substitutes for vinylic halides and tri?ates.12
