References and Notes
1a Current address: Johnson and Johnson Pharmaceutical Research and Development, Chemical Development, Turnhoutseweg 30, 2340, Beerse, Belgium.
1b Current address: CMC Solutions, Overhemstraat 3, 3320 Hoegarden, Belgium.
2
Giri R.
Maugel N.
Li J.-J.
Wang D.-H.
Breazzano SP.
Saunders LB.
Yu J.-Q.
J. Am. Chem. Soc.
2007,
129:
3510
3a
Giles R.
Green IR.
van Eeden N.
Eur. J. Org. Chem.
2004,
4416
3b
Guiso M.
Bianco A.
Marra C.
Cavarischia C.
Eur. J. Org. Chem.
2003,
3407
3c Agejas-Chicharro J, Bueno Melendo AB, Camp NP, Gilmore J, Lamas-Peteira C, Timms GH, and Williams AC. inventors; PCT Int., WO 03053948.
3d
Michaelidis MR.
Schoenleber R.
Thomas S.
Yamamoto DM.
Britton DR.
MacKenzie R.
Kebabian JW.
J. Med. Chem.
1991,
34:
2946
4a For a historical account of the development of the Kumada coupling, see: Tamao K.
J. Organomet. Chem.
2002,
653:
23
For publications with comprehensive references on Pd- and Ni-catalyzed Kumada coupling, see:
4b
Tasler S.
Lipshutz BH.
J. Org. Chem.
2003,
68:
1190
4c
Boelm VPW.
Weskamp T.
Gstoettmayr CWK.
Herrmann WA.
Angew. Chem. Int. Ed.
2000,
39:
1602
4d
Huang J.
Nolan SP.
J. Am. Chem. Soc.
1999,
121:
9889
5 The Grignard, 8, is stable despite the β-alkoxy function but shows remarkably low reactivity. For example, reaction with aldehydes takes place only at 60 °C: Zhou W.
Gumina G.
Chong Y.
Wang J.
Schinazi RF.
Chu CK.
J. Med. Chem.
2004,
47:
3399
6 An extensive screening protocol was conducted. Some examples of the catalysts that were evaluated include: Cl2Ni(PPh3)2, Cl2Ni(dppp), Cl2Ni(dppe) [dppe: 1,2-bis(diphenylphosphino)ethane], Ni(acac)2, Ni(acac)2-Imes+Cl- (Imes: 1,3-dimesitylimidazol-2-ylidene), Ni/C, in THF, Bu2O, toluene, NMP, at 60-80 °C.
7 The catalysts screened include: Pd(PPh)4, Pd(OAc)2-P(cy)3, Pd(OAc)2-Pt-Bu3, PdCl2-dppf [1,1-bis(diphenylphos-phino)ferrocene], Pd2(dba)3-P(tol)3, Pd2(dba)3-P(furyl)3.
8 In the absence of the nitrile Pd-catalyzed coupling of unprotected halobenzoic acid have been reported: Bugamagin NA.
Luzikova EV.
J. Organomet. Chem.
1997,
532:
271
9 Solvent screens with NMP, DMSO, toluene, trifluoro-toluene, MTBE, gave no reaction under these reaction conditions.
10 Attempts to convert 8 into the corresponding Zn, boronic acid or trifluoroborate derivatives, to evaluate its coupling under Pd catalysis, were not successful.
11 Variations on the ratio of 4:9 from 80:20 to 92:8 were observed, reaction time varied between five hours and 24 hours, while the conversion varied more than 20%.
12 Coordination of carboxylates to Pd(II) oxidative addition intermediates has been described in Heck coupling reactions: Dounay AB.
Overman LE.
Chem. Rev.
2003,
103:
2945
13 The product 4 can be isolated in ca 98% purity in 92% yield by crystallization from EtOAc-heptane. The styrene derivative 9 can be thus completely removed.
