-Catalyzed Carbometallation C C C C ML n C C ML n ML n C C C C ML n ML n C C ML n Wipf Group esearch Topic Seminar Juan Arredondo November 13, 2004 Juan Arredondo @ Wipf Group 1 11/14/2004
Carbometallation Term coined for describing chemical processes involving net addition of carbon-metal bonds to carbon-carbon π-bonds. ne of the several patterns for C-C bond formation observable with organotransition-metal complexes along with reductive elimination, migratory insertion, etc. C C C C ML n C C ML n ML n C C C C ML n ML n C C ML n C C ML n C ML n C C ML n Juan Arredondo @ Wipf Group 2 11/14/2004
In 1959, Natta first reported the polymerization of propylene with Ti 4 /Al 3. eaction proceeds with relative asymmetric induction with polymer sections of the same absolute configuration (isotactic). Subsequent work was focused on finding a soluble of group IV metallocene catalyst (Ti,, f). Controlled Monocarbometallation of Alkenes and Alkynes Stereo- and regioselective single-state addition of organometallics species can be a valuable synthetic tool. Normant s carbocupration (1976) was the first example with high selectivity and reasonable generality. Limitations arose from the thermal instability of the alkylcopper reagents and capricious effects of proximal hetereoatoms. 1 Cu. MgX 2 + 2 C C Timeline Schwartz s systematic investigation (1974) of hydrozirconation of alkenes and alkynes with Cp 2 and observations of its addition to alkenes and alkynes by Wales and coworkers. Kaminsky s use of Cp 2 2 and methylaluminoxanes as catalyst for alkene polymerization (1976). Negishi s catalyzed carboalumination with Ti and (1978). 2 2 Cu. MgX 2 Juan Arredondo @ Wipf Group 3 11/14/2004
Carbometallation: FM Analysis Dynamic Polarization LUM M ML n C C ML n C C M LUM Two Lewis acids (or electrophiles) which make one of them more acidic (or electrophilic), while making the other more basic (or nucleophilic). Structural requirement for organometallic reagent is the availability of a low-lying metal empty orbital. 1 M 1 L + 2 L 2 M Carbometallations that proceed via pericyclic reactions can be facile and highly stereoselective. Energy of activation for carbometallation would be higher than that of hydrometallation due greater steric requirements of C groups than. 1 M 1 L 2 L 2 M "ate" complexation permanent polarization 1 M 1 L 2 L 2 M 1 M 2 L + 1 L 2 M dynamic polarization transmetallation 1 M 1 L 2 M δ δ+ 2 L Negishi E., Kondakov, D, Y., Chem. Soc. ev. 1996, 26, 417 Juan Arredondo @ Wipf Group 4 11/14/2004
Zirconium-Catalyzed Carboalumination of Alkynes 1 1 C C + cat. Cp 2 Al 2 3 C 2 2 or C 2 C 2 2 Al 2 2 85-95% 1 2 C CD 3 Al Cp 2 2 D Al 2 2 D 1. n-buli 2. D 2 3 Al Cp 2 2 C C Al 2 D 2 (> 98% Z) D If Cp 2 2 is omitted or aluminumfree Cp 2 is used, only trace amount of the alkene is obtained. I 2 n-buli (~ 96% E) D 2 /TF I Li Negishi, E., et al. J. Am. Chem. Soc. 1978, 100, 2252; J. Am. Chem. Soc. 1978, 100, 2254 Juan Arredondo @ Wipf Group 5 11/14/2004
chanistic Studies 3 Al + Cp 2 2 2 Al Cp 2 C C C C δ+ δ Cp 2 Al 2 Cp 2 Al 2 Al 2 + Cp 2 2 Cp 2 C C 1 X AlX 2 X = and/or 1 1 =, and higher alkyl n Al 3-n + Cp 2 2 (X)Al Cp 2 Y C C C C δ+ δ Al Cp 2 Y X Al X Cp 2 Y AlX + Cp 2 2 n = 3 or 2 X and Y = or C C 2 Al- 2 Cp 2 induced carbometallation Cp 2 (CD 3 ) deuterium incorporation (< 4%) 1 Cp 2 AlX 2 X = and/or 1 1 =, and higher alkyl Negishi, E. et al. J. Am. Chem. Soc. 1978, 100, 2252, J. Am. Chem. Soc. 1981, 103, 4985, J. Am. Chem. Soc. 1985, 107, 6639 Juan Arredondo @ Wipf Group 6 11/14/2004
Synthetic Scope 1 2 Pd,Ni 1 1 2 X + 1 2 Al 3 1 2 g X 2 B' 2 ' " ' " g 2 B' 2 1 2 ' Al 3 [Cu] S N ' S N 2 1 1 Zn 1 ' " 2 Zn 2 X Cu " Juan Arredondo @ Wipf Group 7 11/14/2004
Zirconium-Catalyzed Enantioselective thylalumination of Unactivated Alkenes C C 3 Al + Cp 2 2 C C 2 C C Al 2 CC 2 Al 2 1. 3 Al 8 mol % (1) 2. 2 () 1 Negishi, E., et al. J. Am. Chem. Soc. 1995, 117, 10771 Pure Appl. Chem. 2002, 74, 151 Juan Arredondo @ Wipf Group 8 11/14/2004
Stoichiometric vs. Catalytic Carbometallation Stoichiometric Process n-ex ML n ML n-ex n desired product Catalytic Cycle n-ex ML n n-ex n-ex ML n n-ex minor (~ 20%) C 2 L n C C 2 ML n n-ex n-ctml n β dehydrometallation n-ex n-ct major n-ex n-ct ML n Juan Arredondo @ Wipf Group 9 11/14/2004
Competing eactions Ziegler-Natta Polymerization Cp 2 + P β- elimination P Cp 2 Cp 2 P 2 Cp 2 hydrogen transfer + P 'M transmetalation M ' Cp 2 + P Polymerization and oligomerization β-dehydrometallation leading to -catalyzed hydrometallation -catalyzed cyclic carbometallation of alkenes -centered carbometallation vs. Al- or other metal-centered carbometallation Juan Arredondo @ Wipf Group 10 11/14/2004
chanism C 2 L n C C 2 The use of bulky ligands in (NM) 2 2 or NMI is responsible for suppressing β- transfer hydroalumination. Polymerization is minimized with the use of one equiv. or less of alkene relative to the alkylalane reagent. 3 Al dissociative path * * * = 3 Al associative path * * Al Al * * Negishi, E. In Catalytic Asymmetric Synthesis, jima (Ed), 2000, p.165 Juan Arredondo @ Wipf Group 11 11/14/2004
chanisms of Carboalumination and related reactions Negishi, E. Pure Appl. Chem. 2001, 73, 239 Juan Arredondo @ Wipf Group 12 11/14/2004
Dzhemilev hylmagnesiation of Alkenes (monometallic cyclic) Cp 2 MgBr Cp 2 MgBr Cp 2 MgBr eaction failed with methylmagnesium derivatives Dzhemilev, U., M. uss. Chem. ev. 2000, 69,121 Juan Arredondo @ Wipf Group 13 11/14/2004
-Catalyzed Enantioselective hylalumination 10 % Cp 2 2 C 2 2, 23 C n-ct Al 2 + n-ct <5% Al 2 + n-ct + n-ct n-decyl + n-ct n-ct + 3 Al 10% ) 2 2 C 2 2, 23 C n-ct Al 2 2 n-ct >85% 10% ( 5 C 5 ) 2 2 C 2 2, 23 C no reaction ( n-ct recovered >90%) 1. 3 Al Cp 2 2, (C 2 ) 2 2. D, D 2 n-ct D + n-ct + n-ct D n-ct 3 Al, (1) C 3 C 2 n-ct 37% 20% 20% [] n-ct Al 64%, 92% ee 1 Negishi, E., et al. J. Am. Chem. Soc. 1996, 118, 1577 Juan Arredondo @ Wipf Group 14 11/14/2004
hyl-alumination of Monosubstituted Alkenes 1. 3 Al Cp 2 2, (C 2 ) 2 2. D, D 2 n-ct D + n-ct + n-ct D n-ct 37% 20% 20% 3 Al, (1) C 3 C 2 n-ct Al [] n-ct 64%, 92% ee 1 Enantioselectivity (thyl vs. hyl) Negishi, E., et al. J. Am. Chem. Soc. 1996, 118, 1577; Pure Appl. Chem., 2001, 73, 239 Juan Arredondo @ Wipf Group 15 11/14/2004
Solvent & Temperature Effect 3 Al, 1 hexanes n-ct Al 2 n-ct n-ct 65%, 33%ee 3 Al, 1 C 3 C 2 n-ct Al 2 n-ct 63%, 92%ee 1 Negishi, E., et al. J. Am. Chem. Soc. 1996, 118, 1577 Juan Arredondo @ Wipf Group 16 11/14/2004
Synthetic Applications ydrometallation/alkylalumination Tandem Process Negishi, E. et al. Angew. Chem. Int. Ed. 2002, 41, 2141 Juan Arredondo @ Wipf Group 17 11/14/2004
Synthetic Applications N Scyphostatin Z 1. 3 Al 5% (±) [ 2 (nmi) 2 ] MA C 2 2, 0 o C 2. 2 Z + Z (2S,4) (2,4) Negishi, E. et al. Angew. Chem. Int. Ed. 2004, 43, 2911 Juan Arredondo @ Wipf Group 18 11/14/2004
Synthetic Applications 6,7-dehydrostipiamide Negishi, E. et al. rg. Lett. 2004, 6, 1425 N C C Ac P 2 Zaragozic Acid A Vitamin E Negishi, E. et al. rg. Lett. 2001, 3, 3253 2 1 1 = C 6 8 () 5 or C 5 7 () 4 2 = or Ac TMC-151 A-F Negishi, E. et al. PNAS, 2004, 43, 5782 Juan Arredondo @ Wipf Group 19 11/14/2004
Carbometallation of α,ω-dienes Cp* 2 2 B(C 6 F 5 ) 3 Al 3 Al 2 1.Air X Toluene, 0 C X 2. Aq. N 4 X lefin Proudct % Yield Selectivity 62 66 % trans 67 78 68% trans 70% cis 63 55 %ee Chlorinated solvents (DCM, DCE) Improved reaction rates. chanism not fully understood, perhaps a cationic process. 78 58 66 %ee 63 % ee TBS 7 TBS 7 53 53 % ee Waymouth,., J. Am. Chem. Soc. 1995, 117,5873; rganometallics, 1998, 17, 5728 Juan Arredondo @ Wipf Group 20 11/14/2004
Carbomagnesation-Elimination f Cyclic Alkenes Mg 1. n-prmg cat. Cp 2 Ti 2 2 N Cat. 2. Br cat. 2 Ni(P 3 ) 2 3. TPAP, NM 2 C N Sch 38516 (Fluvirucin B 1 ) Substrate of Mg Product Yield, % % ee 65 >97 2 2 Mg N N 75 >95 73 95 C 2 2 C L 2 oveyda A. et al. J. Am. Chem. Soc. 1993, 115, 6997 J. Am. Chem. Soc. 1995, 117, 2943 (s) Mg n= 0-2 n-pr, n-bu 75 92 35-40 >95 Juan Arredondo @ Wipf Group 21 11/14/2004
Carboalumination-Elimination Tandem eaction of Allylic Derivatives 3 Al 1 or 2 r.t 6-20 h Al + Al 2 2 / D 2 (D) 1. 2 2. 2 1 or 2 M E + E 1 M Cat. E + Solvent % Yield % ee N Mg 2 SS 2 90 81 N 2 Mg 2 SS TF 95 75 N NCy S 2 Mg Mg 3 Al 1 2 2 SS SS 2 TF 2 hexane 39 87 76 26 83 64 2 Mg 2 Mg 2 1 2 2 TF TF 75 27 56 27 2 Whitby,., et al. Tetrahedron Lett. 1997, 38, 2335; Tetrahedron Lett. 1998, 54, 14617 Juan Arredondo @ Wipf Group 22 11/14/2004
Wipf Group Contributions Water-Accelerated Carboalumination 1. Al 3 (2 equiv) Cp 2 2 (0.2 equiv) 2 (1.5 equiv) nc 6 13 nc 6 13 C 2 2, -70 C 310 h, min, 100% 100% 2. 3 N nc 6 + 13 97:3 95:5 Al 3 [Cp 2 2 ] - Al 2 T < 0 C Al Al 3 T > 0 C Al Al slow ' C C fast ' Al 2 Wipf et al. Angew. Chem. Int. Ed. 1993, 32, 1068 Juan Arredondo @ Wipf Group 23 11/14/2004
Asymmetric thylalumination of α-lefins Pitiamide A N 1. 3 Al (1-4 eq), C 2 2, 0 C, rt, or 40 C, 12-24h N Ns N + + M =, TIPS, Bn 2. Air 1 (5 mol%) 1. 3 Al (4-5 eq), 1 (5 mol%) Additive C 2 2, -20 C,12-24 h 2. Air 1; M = Li, Al 2 Kinetic Analysis of -carboalumination of Styrene Yield ee% TBDPS 85/88 80/80 TBDPS(C 2 ) 4 73/83 75/81 C 3 (C 2 ) 5 35/78 75/81 c-c 6 11 94/82 55/74 Additives 2 (1 eq) MA (1.2 eq) none Wipf et al. J. Am. Chem.Soc. 2000, 122, 4608 ; rg. Lett. 2000, 2, 1713 Juan Arredondo @ Wipf Group 24 11/14/2004
Tandem aisen earrangement-asymmetric Carboalumination 1. Al 3 (4 eq.) Additive (1 eq.) C 2 2, 60 min, -20 C + 2. 3 + Additives 2 (94%) MA (85%) none (trace) Thermal Conditions 5.6 : 1 MA catalysis 2.4 : 1 2 catalysis 1.8 : 1 1. 3 Al, 2, C 2 2 2. Air 5 mol% 75%, 75% ee Significant improvement in regioselectivity in favor of the para-aisen product was observed. chanism origin is attributed to a transient strong Lewis acid related, but not identical to MA. Structure of active species remains to be elucidated. Wipf et al. rg Lett. 2001, 3, 1503 ; Adv. Synth. Catal. 2002, 344, 434 Juan Arredondo @ Wipf Group 25 11/14/2004
Sulfinimine Addition and Asymmetric Synthesis of Allylic Amines 1. Al 3 (2 equiv.), Cp 2 2 (0.03 equiv.), 2 (1 equiv.), C 2 2, 0 C, 40 min 2 Al S ' N -15 C S ' N = C 6 13,, t-bu, Bu TIPS(C 2 ) 3 ' = () (S)(p-), (t-bu) (p-) S N (p-) S N (p-) S N C 6 13 TIPS 80%, 90% de 76%, 90% de 75%, 78% de S (p-) N 1. Amberlite I-120, 5 h 2. N 4,, 8h; 90% 3. Ac, 3 N, DMAP, C 2 2, 1h; 94% NAc 3, Na, /C 2 2, -78 C, 1 h; 72% NAc C 2 Wipf, et al. elv. Chim. Acta 2002, 85, 3478 Juan Arredondo @ Wipf Group 26 11/14/2004
further optimization, especially with respect to chiral zirconocene catalyst, is desirable, Negishi, E. In Catalytic Asymmetric Synthesis, jima (Ed), 2000, p. 170, Wiley, New York Further improvements in % ee will depend on the development of more effective zirconocene catalyst Wipf et al. rg. Lett. 2001, 3, 1503 2 Juan Arredondo @ Wipf Group 27 11/14/2004