Enantioselective Synthesis of Biaryl Compounds via Suzuki–Miyaura Cross-Coupling Using a Palladium Complex of 7′-Butoxy-7-(diphenylphosphino)-8,8′-biquinolyl: Investigation of a New Chiral Ligand Architecture

Abstract

7,7′-Dihydroxy-8,8′-biquinolyl was converted to the title phosphine in four-steps via Mitsunobu monoetherification, trifylation, phosphination, and phosphine oxide reduction (63% overall yield). Enantiomerically pure phosphine was combined with Pd₂dba₃ and investigated for the synthesis of axially chiral biaryl compounds from Ar¹Br and Ar²B(OH)₂ in the presence of K₃PO₄ in toluene solvent (6 examples, 4–97% yield, 4–74% ee). The analogous carbocyclic ligand 2-(diphenylphosphino)-2′-methoxy-1,1′-binaphthyl (MOP) was studied for comparative purposes and found to be effective for the synthesis of hindered 2,2′-disubstituted 1,1′-binaphthyls (78–83% yield, 20–38% ee).

Key words

asymmetric catalysis - atropisomerism - azaBINOL - cross-coupling - quinolines

• References


For reviews on 1,1′-bi-2-naphthol (BINOL) and general discussion of 1,1′-binaphyls, see:
• 1a Brunel JM. Chem. Rev. 2005; 105: 857
• 1b Chen Y, Yekta S, Yudin AK. Chem. Rev. 2003; 103: 3155
• 1c Pu L. Chem. Rev. 1998; 98: 2405

For reviews on 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (BINAP), see:
• 2a Berthod M, Mignani G, Woodward G, Lemaire M. Chem. Rev. 2005; 105: 1801
• 2b Noyori R, Takaya H. Acc. Chem. Res. 1990; 23: 345
• 3a Alcock NW, Brown JM, Hulmes DI. Tetrahedron: Asymmetry 1993; 4: 743
• 3b Lim CW, Tissot O, Mattison A, Hooper MW, Brown JM, Cowley AR, Hulmes DI, Blacker AJ. Org. Process Res. Dev. 2003; 3: 379
• 3c Knopfel TF, Aschwanden P, Ichikawa T, Watanabe T, Carreira EM. Angew. Chem. Int. Ed. 2004; 43: 5971
• 3d Cardoso FS. P, Abboud KA, Aponick A. J. Am. Chem. Soc. 2013; 135: 14548

For background on the chemistry of 8,8′-biquinolyls and leading references, see:
• 4a Blakemore PR, Kilner C, Milicevic SD. J. Org. Chem. 2006; 71: 8212
• 4b Milicevic SS, Wang C, Zakharov LN, Blakemore PR. Eur. J. Org. Chem. 2012; 3249

For selected notable examples, see:
• 5a Zhou T, Peters B, Maldonado MF, Govender T, Andersson PG. J. Am. Chem. Soc. 2012; 134: 13592
• 5b Mei L.-y, Yuan Z.-l, Shi M. Organometallics 2011; 30: 6466
• 5c Noël T, Bert K, Van der Eycken E, Van der Eycken J. Eur. J. Org. Chem. 2010; 4056
• 5d Meng X, Li X, Xu D. Tetrahedron: Asymmetry 2009; 20: 1402
• 5e Schönleber M, Hilgraf R, Pfaltz A. Adv. Synth. Catal. 2008; 350: 2033
• 5f Lightfoot A, Schnider P, Pfaltz A. Angew. Chem. Int. Ed. 1998; 37: 2897
• 6 Wang C, Flanigan DM, Zakharov LN, Blakemore PR. Org. Lett. 2011; 13: 4024
• 7a Mitsunobu O, Yamada M. Bull. Chem. Soc. Jpn. 1967; 40: 2380
• 7b Hughes DL. Org. React. 1992; 42: 335

The predominant formation of phosphine oxides rather than phosphines via Pd(0)-catalyzed phosphination with Ph₂PH from aryl triflates has been previously noted, see:
• 8a Kurz L, Lee G, Morgans D, Waldyke MJ, Ward T. Tetrahedron Lett. 1990; 31: 6321
• 8b Martorell G, Garcías X, Janura M, Saá JM. J. Org. Chem. 1998; 63: 3463
• 9 Crystallographic data for (±)-7 have been submitted to the Cambridge Crystallographic Data Centre with deposition number CCDC 965683. Copies of the data may be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK [fax: [phone] or e-mail: [e-mail]].
• 10 As defined for polarimetry readings taken from CHCl₃ solution at 589 nm. All other signs of optical rotation indicated herein are likewise defined.

Exciton coupling between the long-axes polarized ¹B_b transitions of biquinolyl (+)-7 was revealed as a weak bisignate band of positive chirality phase. The couplet was composed of a positive maximum Cotton effect at 242 nm and a corresponding negative minimum at 231 nm (ΔΔε = +6.8 M^–1 cm^–1 at >98% ee). For discourse on exciton coupling in the biaryl series, see:
• 11a Mason SF, Seal RH, Roberts DR. Tetrahedron 1974; 30: 1671
• 11b Rodger A, Nordén B. Circular Dichroism and Linear Dichroism . Oxford University Press; New York: 1997
• 11c Berova N, Nakanishi K In Circular Dichroism: Principles and Applications . Berova N, Nakanishi K, Woody RW. Wiley-VCH; New York: 2000
• 12a Uozumi Y, Hayashi T. J. Am. Chem. Soc. 1991; 113: 9887
• 12b Uozumi Y, Tanahashi A, Lee S.-Y, Hayashi T. J. Org. Chem. 1993; 58: 1945
• 12c Uozumi Y, Kawatsura M, Hayashi T. Org. Synth. 2002; 78: 1
• 13a Naumann K, Zon G, Mislow K. J. Am. Chem. Soc. 1969; 91: 7012
• 13b Horner L, Balzer WD. Tetrahedron Lett. 1965; 1157
• 14 No significant change in optical rotation was noted for a sample of enantioenriched (+)-(aR)-2 after it was heated for 15 h at reflux (110 °C) in toluene solvent under argon.
• 15a Miyaura N, Suzuki A. J. Chem. Soc., Chem. Commun. 1979; 866
• 15b Miyaura N, Suzuki A. Chem. Rev. 1995; 95: 2457
• 15c Lennox AJ. J, Lloyd-Jones GC. Angew. Chem. Int. Ed. 2013; 52: 7362
• 16a Cammidge AN, Crépy KV. L. Chem. Commun. 2000; 1723
• 16b Yin J, Buchwald SL. J. Am. Chem. Soc. 2000; 122: 12051
• 16c Shen X, Jones GO, Watson DA, Bhayana B, Buchwald SK. J. Am. Chem. Soc. 2010; 132: 11278

Enantioselectivity in the synthesis of biaryls via Suzuki–Miyaura coupling is typically no higher than 90% ee, for some rare exceptions see ref. 16b, and:
• 17a Bermejo A, Ros A, Fernández R, Lassaletta JM. J. Am. Chem. Soc. 2008; 130: 15798
• 17b Uozumi Y, Matsuura Y, Arakawa T, Yamada YM. A. Angew. Chem. Int. Ed. 2009; 48: 2708
• 17c Yamamoto T, Akai Y, Nagata Y, Suginome M. Angew. Chem. Int. Ed. 2011; 50: 8844
• 17d Wang S, Li J, Miao T, Wu W, Li Q, Zhang Y, Zhou Z, Qiu L. Org. Lett. 2012; 14: 1966
• 17e Tang W, Patel ND, Xu G, Xu X, Savoie J, Ma S, Hao M.-H, Keshipeddy S, Capacci AG, Wei X, Zhang Y, Gao JJ, Li W, Rodriguez S, Lu BZ, Yee NK, Senanayake CH. Org. Lett. 2012; 14: 2258
• 17f Zhou Y, Wang S, Wu W, Li Q, He Y, Zhuang Y, Li L, Pang J, Zhou Z, Qiu L. Org. Lett. 2013; 15: 5508
• 18 Comparing the data in Table 1 for entries 3, 8, and 9, one may conclude that (+)-2 accelerates cross-coupling while its oxide (–)-7 has a retardation effect. For the consequences of chiral ligand exchange and acceleration/retardation effects on metal-mediated asymmetric catalysis, see: Berrisford DJ, Bolm C, Sharpless KB. Angew. Chem., Int. Ed. Engl. 1995; 34: 1059
• 19 Biaryl 11 was prepared in 36–64% yield and 77–84% ee by Lassaletta et al. using a chiral bis-hydrazone ligand (ref. 17a), while 12 was obtained in 85% yield and 75% ee by Putala and Meskova using 1′-(2,6-dimethoxyphenyl)-1-(diphenylphosphino)-1,1′-binaphthyl as ligand (at 65 °C for 3 d), see: Meskova M, Putala M. Tetrahedron: Asymmetry 2013; 24: 894
• 20 Qiu et al. obtained 70–75% yield and 46–78% ee in the synthesis of biarylphosphonates by applying essentially the same MOP based conditions as utilized here, see references 17d and 17f. In addition, Fujihara et al. obtained 50% yield and 12% ee in the synthesis of 2-methoxy-1,1′-binaphthyl via Suzuki–Miyaura cross-coupling using Pd-nanoparticles in the presence of MOP, see: Sawai K, Tatumi R, Nakahodo T, Fujihara H. Angew. Chem. Int. Ed. 2008; 47: 6917

The 2′-MeO group in MOP (3) does not play a direct ligating role in Pd·MOP complexes; however, short Pd-C1′ contacts have been noted by XRD analysis in some complexes indicating that the description of MOP as a strict monodentate ligand is an over simplification; see, for example:
• 21a Dotta P, Kumar PG. A, Pregosin PS. Organometallics 2003; 22: 5345
• 21b Dotta P, Kumar PG. A, Pregosin PS, Albinati A. Helv. Chim. Acta 2004; 87: 272
• 21c Hayashi T, Iwamura H, Uozumi Y, Matsumoto Y, Ozawa F. Synthesis 1994; 526
• 22 Yin J, Rainka MP, Zhang X.-X, Buchwald SL. J. Am. Chem. Soc. 2002; 124: 1162
• 23 In these experiments, care was taken to ensure that the phoshine ligand (+)-(aR)-2 was not contaminated by its phosphine oxide (–)-(aR)-7.

For application of MOP in other Suzuki–Miyaura cross-coupling reactions not involving the atroposelective formation of biaryls, see:
• 24a Willis MC, Powell LH. W, Claverie CK, Watson SJ. Angew. Chem. Int. Ed. 2004; 43: 1249
• 24b Brath H, Meskova M, Putala M. Eur. J. Org. Chem. 2009; 3315
• 25 Pangborn AB, Giardello MA, Grubbs RH, Rosen RK. Organometallics 1996; 15: 1518
• 26 SHELXTL Software Reference Manual Version 6.10 . Bruker Analytical X-ray System, Inc; Madison (WI, USA): 2000
• 27 Tu T, Sun Z, Fang W, Xu M, Zhou Y. Org. Lett. 2012; 14: 4250