Fischer Carbene Complexes in Organic Synthesis 1 A. B. Charette J. Am. Chem. So
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Fischer Carbene Complexes in Organic Synthesis 1 A.B. Charette J. Am. Chem. Soc. 2001, 123, 11829. Baran Group Meeting 1/31/2007 Ke Chen German inorganic chemist. Born in Munich on November 10, 1918. Studied at Munich Technical University and spent his career there. Became director of the inorganic chemistry institute in 1964. In the 1960s, discovered a metal alkylidene and alkylidyne complexes, referred to as Fischer carbenes and Fischer carbynes. Shared the Nobel Prize in Chemistry with Geoffery Wilkinson in 1973, for the pioneering work on the chemistry of organometallic compounds. Ernst Otto Fischer (1918 - ) Isolation of first transition-metal carbene complex: (CO) 5 W CO LiMe (CO) 5 W Me O CH 2 N 2 (CO) 5 W Me OMe E. O. Fischer, A. Maasbol, Angew. Chem. Int. Ed., 1964, 3, 580. Representative Fischer Carbenes: Me OMe W(CO) 5 Ph Ph Cr(CO) 5 Ph NEt 2 Fe(CO) 4 Ph OTiCp 2 Cl Mn(CO) 2 (MeCp) Me OMe Co(CO) 3 SnPh 3 Comparision of Fisher Carbene and Schrock carbene: Schrock carbenes are found with: high oxidation states early transition metals Ti(IV), Ta(V) non pi-acceptor ligands non pi-donor substituents Schrock carbene, named after Richard R. Schrock, is nucleophilic at the carbene carbon atom in an unpaired triplet state. Representatives: Cp 2 Ta CH 2 CH 3 Fischer carbenes are found with : low oxidation state metals; middle and late transition metals Fe(0), Mo(0), Cr(0), W(0); pi-electron acceptor metal ligands; pi-donor substituents on methylene group such as alkoxy and amino groups. Persistent carbenes, isolated as a crystalline solid by Anthony J. Arduengo in 1991, can exist in the singlet state or the triplet state. Foiled carbenes were defined as "systems where stabilization is obtained by the inception of the facile reaction which is foiled by the impossibility of attaining the final product geometry". They only exist in the singlet state. Other Types of Stabilized Carbenes: Rolf Gleiter, Ronald Hoffman J. Am. Chem. Soc. 1968, 90, 5457 - 5460. Jean-Luc Mieusset and Udo H. Brinker J. Am. Chem. Soc. 2006, 128, 15843 - 15850. Fischer Carbene Complexes in Organic Synthesis 2 Baran Group Meeting 1/31/2007 Ke Chen Advantages over regular carbenes - From fleeting intermediates to powerful reagents 1. Improved stability Typical carbenes such as diphenyl carbene have lifetimes in the nanosecond regime. Most Fischer carbene complexes are stable to air and water and to dilute acids and bases. Despite the high dipole moment of these complexes (~ 4 - 5 Debye), most complexes can be purified by chromatography on silica gel with hexane as eluent and are usually the first compounds to elute. Identification of the fractions from the column containing the carbene complex can simply be done by eye on the basis of their color. The colors of complexes bearing alkoxy groups as the heteroatom-stabilizing group tend to correlate with the hybridzation of the carbon substituent of the carbene carbon. Those with sp 3
2 carbons are normally red and those with sp hybridized carbon substituents are invariably an intense purple/black color. 2. Excellent functional group compatibility - serving as blocking groups in organic synthesis. J. Barluenga. J. Am. Chem. Soc. 2002, 124, 9056 -9057. 3. Improved reactivity and selectivity MeO Cr(CO) 5 RT, 3 h 70 % MeO Cr(CO) 5 MeO Cr(CO) 5 MeO O thermal conditions: RT, 7 months, 54 % MeO O MeO O 92 : 8 70 : 30 W. Wulff. J. Am. Chem. Soc. 1990, 112, 3642. http://www.chemistry.msu.edu/faculty/wulff/myweb 26 /research/carbenes.htm AlCl 3 , 0.5 h , 50 % 95 : 5 [Cr] OMe Ph OTMS Et Ph O [Cr] OMe Et O [Cr] Ph Et H H BuLi, THF, -78 o C 75 % 3 equiv of CH 2 CHCH 2 Li, THF -78 o C to RT, then SiO 2 71 % Fischer Carbene Complexes in Organic Synthesis 3 Baran Group Meeting 1/31/2007 Ke Chen Synthesis of Fischer carbene complexes: 1. Standard Fischer route M(CO) 6 R 1 Li (OC) 5 M OLi R 1 RX (OC) 5 M OR 2 R 1 HN R 3 R 4 HS R 3 (OC) 5 M SR 3 R 1 (OC) 5 M NR 3 R 4 R 1 M = Cr, Mo, W R 1
RX = R 2 3 O + BF 4 - , R 2 OSO
3 F R 3 , R
4 = H, alkyl (OC) 5 M OLi R 1 Me 4 N + Br - (OC) 5 M O - NMe 4 + R 1 X R 2 O (OC) 5 M O R 1 R 2 O R 3 OH (OC) 5 M OR 3 R 1 M = Cr, W R 1
R 2 = Me, tBu X = Br, Cl R 3 = terpene, sugar skeletons 2. Hegedus-Semmelhack approach M(CO) 6 C 8 K K 2 [M(CO) 5 ] R 1 Cl O (OC) 5 M OK R 1 R 2 X (OC) 5 M OR 2 R 1 (OC) 5 M O - R 1 R 1 NR 3 R 4 O NR 3 R 4 TMSCl (OC) 5 M NR 3 R 4 R 1 M = Cr, W R 1
This is the most direct and general approach to Fischer carbene complexes; Limitations are the availability of organolithium compound and the alkylation reagent. This is the standard approach to optically active Fischer carbene complexes bearing alkoxy substituents. R 2 X = R 2 3 O + BF 4 - , R 2 OSO
3 F R 3 , R
4 = H, alkyl This strategy combining an organoelectrophile and a metal nucleophile can be extended to the synthesis of aminocarbene complexes. Recent reviews: W. D. Wulff, in Comprehensive Organometallic Chemistry II, ed. A. W. Abel, F. G. A. Stone and G. Wilkinson, pergamon Press, Oxford, 1995, vol. 12, p. 469 L. S. Hegedus, ibid., vol. 12, p. 549. Fischer Carbene Complexes in Organic Synthesis 4 Baran Group Meeting 1/31/2007 Ke Chen Reaction pattern of carbene complexes: OC Cr CO OC OC CO CR 2 O R H E Nu B C A B (OC) 5 M OR R (OC) 5 M OR R Part I: Ligand-centered Pattern A: Addition of nucleophiles (OC) 5 Cr OMe Ph NH 2 R (OC) 5 Cr OMe Ph NHR H (OC) 5 Cr NHR Ph - MeOH (OC) 5 Cr OMe Ph N MeO Ph Cr(CO) 5 N ? (OC) 5 Cr OMe O Ph OLi Li O O Ph Cr(CO) 5 THF, -80 o C to RT 50 % J. Barluengal, J. Chem. Soc., Chem. Commun. 1993, 1068 H. Fischer, Chem. Ber. 1980, 113, 193
W. Wulff, J. Org. Chem., 1994, 6882. B. A. Anderson, J. Am. Chem. Soc., 1993, 115, 4602. For reviews on reaction pattern of carbene complexes, see "Carbene Chemistry : From Fleeting Intermediates to Powerful Reagents", chapter 8.
5 Baran Group Meeting 1/31/2007 Ke Chen Reaction pattern of carbene complexes: Part I: Ligand-centered Cycloaddition reactions: [2 + 2] (OC) 5 W OMe CH 3 OMe RT, 12 h 87 % CH 3 OMe (OC) 5 W H 3 CO [3 + 2] K. L. Faron, J. Am. Chem. Soc. 1988, 110, 8727 -8729. (OC) 5 W OMe CH 3 TMSCHN 2 hexanes, RT 4.5 h, 87 % (OC) 5 W OMe N NH H 3 C W. D. Wulff, J. Am. Chem. Soc. 1986, 108, 5229 -5236. [4 + 2] (OC) 4 Cr N N O H 3 C Ph CH 3 DCM, RT, 12 h 80 %,single isomer CH 3 OCH 3 TBSO (OC) 4 Cr N N O H 3 C Ph CH 3 OTBS CH 3 CH 3 O W. D. Wulff, J. Am. Chem. Soc. 1997, 119, 6438 -6439. Diels-Alder reaction of boroxycarbene complexes: Br N 1. t-BuLi, Et 2 O 2. Cr(CO) 6 , Et 2 O 3. BF 3 . Et 2 O, RT N B O F F (OC) 5 Cr N Me Ph 1.THF, -78 o C to RT 85% 2. 3N HCl, THF, RT 95 % N B O F F (OC) 5 Cr O HBr, DCM, RT 85 % CHO N O J. Barluenga. J. Am. Chem. Soc. 1998, 120, 2514 -2522. Intramolecular Pauson -Khand reaction: (OC) 5 W NH Ph [Co 2 (CO) 8 ] 75 % (OC) 5 W Ph O J. M. Moreto. Angew. Chem. Int. Engl. 1991, 11,1470. Fischer Carbene Complexes in Organic Synthesis Miscellaneous cases (OC) 5 W OLi (-) -Ipc 2 BCl, Et 2 O -78 o C to RT B O H Ipc H 2 O 2 , NaOH 83 %, > 99 % de Ph Ph OH OH Ph J. Barluenga, J. Am. Chem. Soc,, 1996, 118, 6090 -6091. 6 Baran Group Meeting 1/31/2007 Ke Chen Reaction pattern of carbene complexes: Part II: Metal-centered (OC)
5 Cr OR 1 R 2 (OC) 4 Cr OR 1 R 2 (OC)
4 Cr R 2 OR 1 Olefin Metathesis Cyclopropanation 1. Reaction with olefins "The functionalized Ru Fischer-type complexes are active in a variety of olefin metathesis reactions, although with significantly lower rates than the corresponding carbon analogues." General carbene complexes used in cyclopropanation reactions: Fe Cp OC R*Ph 2 P H Me Fe Cp CH 2 OC OC Cr(CO) 5 Me OMe W(CO) 5 Ph OMe W(CO) 5 Ph H Mo(CO) 5 Bu OMe Cr(CO) 5 Ph OMe Cr(CO) 5 OMe (leads to olefin metathesis product) (less stable ) Suitable olefins: EWG EWG Alkyl EWG Alkyl R 2 R 1 R 2 R 1 R 1 , R 2 = akyl, aryl R 2 R 1 R 3 R 1 , R 2 and R 3 = alkyl requires stronger electrophilic metal carbenes R, H. Grubbs, Organometallics. 2002, 21, 2153 -2164. Cr(CO) 5 Me OMe Et THF, 100 o C 55 % Me MeO H Et Cr Et MeO H R (CO) 4 H R Et MeO Cr(CO) 4 Cr MeO Et H R (CO) 4 H R MeO Et Cr(CO) 4 Me MeO H Et J. Am. Chem. Soc. , 113, 23, 1991, 8916-8921 (OC) 5 Cr OMe Fe DMF, 152 o C 88 %, 97 % de Fe H OMe Cr(CO) 5 OMe O Cl 85 o C,12 h O O O Chemtracts - Organic Chemistry. 17, 67 -71, 2004 Fischer Carbene Complexes in Organic Synthesis 85 % intermediate A favored disfavored O 7 Baran Group Meeting 1/31/2007 Ke Chen D. L. Boger, J. Am. Chem. Soc,, 1995, 11839. Fischer Carbene Complexes in Organic Synthesis 2. Benzannulation (Dotz reaction) OMe Cr(CO) 5 OMe Cr(CO) 4 R S R L OMe Cr(CO) 4 R S R L OMe R S R L Cr OC CO OC CO minimization of interaction OMe R S O R L O R L R S OMe Cr(CO) 3 Cr(CO) 3 HO R L R S OMe Cr(CO) 3 Reaction pattern of carbene complexes: Part II: Metal-centered Suitable metal: Cr (metal of choice) Mo ( furan formation occasionally) W (favor 3 + 2 cycloaddtion) Mg (low yields) Compatible substitution pattern: Aryl carbenes with various substituents Naphthyl and heteroaryl carbenes Vinyl carbenes bearing alkyl substituents Electron - neutral alkynes with various substituents OMe Cr(CO) 5 O O ether, reflux OMe O O nPr O OH 51 % (OC) 5 Cr OMe OCPh 3 TBSCl, hunig base OTBS OCPh 3 Cr(CO) 3 > 92 % d. e. MeO O O Cr(CO) 5 OMe O O N EtO TBSO OTBS O O MeO O O OMe OH OTBS N OTBS BnO EtO fredericamycin A OMe BnO 35 % M. F. Semmelhack, Tetrahedron, 1985, 5803. W. D. Wulff, J. Am. Chem. Soc,, 1994, 116, 6449. - CO + CO 8 Baran Group Meeting 1/31/2007 Ke Chen Fischer Carbene Complexes in Organic Synthesis 3. General Annulation of Fischer carbenes with alkynes and alkenes: Reaction pattern of carbene complexes: Part II: Metal-centered (OC) 5 Cr CH 3 OMe O Ph C 3 H 7 THF, 105 o C, 15h O CH 3 OMe CH 3 Ph O O CH 3 OMe CH 3 Ph O 48 % 18 % J. Am. Chem. Soc. 1991, 113, 5459 - 5461 (OC) 5 Cr CH 3 OMe O Me MeO O OMe Me 13 % 10 % Organometallics, 1990, 9, 3014 - 3015 CO 2 Et (OC) 5 Cr CH 3 OMe H Bu OMe CO 2 Et 66 % J. Am. Chem. Soc. 1994, 116, 6719 - 6732 (OC) 5 Cr Ph OMe O O THF, 70 o C, 24 h CO, 73 %, d. r. = 3 :1 O O OMe Ph H J. Am. Chem. Soc. 1992, 114, 10665 - 10666 (OC) 5 Mo OMe Me Ph O CH 3 THF, 70 o C, 14 h, 40 % O CH 3 Ph O CH 3 OMe J. Am. Chem. Soc. 1990, 112, 1645 - 1647 (OC) 5 Cr OEt SiMe 3 NMe 2 Ph THF 3 EtO Ph Ph Ph NMe 2 EtO Ph Ph Ph NMe 2 64 : 36 Angew. Chem. 1999, 111, 1369 (OC) 5 Cr OMe Ph Me Me TMSO OTMS THF, 90 o C 71 % O O Ph Ph MeO Me Me J. Barluenga, Org. Lett., 2006, 8, 2703 -2706. 9 Baran Group Meeting 1/31/2007 Ke Chen Fischer Carbene Complexes in Organic Synthesis State of art: Group 6 metal carbenes in catalytic carbene transfer reactions (OC) 5 M R OMe M = Cr, W stable, storable, less reactive L n M R OMe M = Pd, Cu, Rh reactive, unstable multi-faced chemistry (OC) 5 Cr O O 1. [Cu(MeCN) 4 ][PF 6 ], DCM 2. DCM, Et 2 O Cu O O Et 2 O MeCN PF 6 J. Barluenga, Angew. Chem. Int. Ed., 2001, 40, 3392. (OC) 5 Cr NMe 2 Br CO 2 Me 2 mol %Pd(OAc) 2 , Et 3 N THF, reflux, 8 h, 80 % O CO 2 Me Br M. A. Sierra, J. Am. Chem. Soc., 2001, 123, 851 -861. Louis S. Hegedus William D. Wulff Daniel F. Harvey Jose Barluenga Download 138.07 Kb. Do'stlaringiz bilan baham: 
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