Scalable Synthesis of 1,3,4,5-Tetraaryl Imidazolium Salts as Precursors of Sterically Demanding N-Heterocyclic Carbenes

Abstract

A convenient, large-scale, and cost-efficient synthesis of 4,5-diarylsubstituted N,N-diarylimidazolium salts is described. A variety of 1,3,4,5-tetraaryl imidazolium salts with increasing electron donation and steric bulk of the N-aryl groups was synthesized in good yields. In the key step, readily available N,N′-diarylthioureas and benzoin/anisoin are coupled to give imidazole-2-thiones, followed by imidazolium salt formation by oxidative desulfurization. In this way, N,N-diarylimidazolium salts with 2-methoxy, 2-methyl, and 2-isopropyl substituents could be obtained; the synthesis of their 2-tert-butyl, 2,6-dimethyl, and 2,6-diisopropyl analogues failed.

Key words

carbene ligands - heterocycles - imidazolium salts - imidazolin­thiones - thioureas

• References

• 1 Current address: C. Azap, Chemetall GmbH, Trakehner Str. 3, 60487 Frankfurt am Main, Germany.
• 2 Current address: A. Christoffers, Diapharm Analytics GmbH, Würzburger Str. 2, 26121 Oldenburg, Germany.
• 3a Herrmann W. A. Kocher C Angew. Chem., Int. Ed. Engl.; 1997, 36: 2163 ; Angew. Chem. 1997, 109, 2256
• 3b Bourissou D, Guerret O, Gabbai FP, Bertrand G. Chem. Rev. 2000; 100: 39
• 3c N-Heterocyclic Carbenes in Transition Metal Catalysis. Glorius F. Springer; Berlin: 2007
• 3d Diez-Gonzalez S, Marion N, Nolan SP. Chem. Rev. 2009; 109: 3612
• 3e Corberán R, Mas E, Peris-Marzá E. Eur. J. Inorg. Chem. 2009; 1700
• 3f Hopkinson MN, Richter C, Schedler M, Glorius F. Nature 2014; 510: 485
• 3g N-Heterocyclic Carbenes: Effective Tools for Organometallic Synthesis. Nolan SP. Wiley-VCH; Weinheim: 2014
• 3h N-Heterocyclic Carbenes: From Laboratory Curiosities to Efficient Synthetic Tools. Diez-Gonzalez S. Royal Society of Chemistry; Cambridge: 2017
• 4 Occhipinti G, Bjørsvik H.-R, Jensen VR. J. Am. Chem. Soc. 2006; 128: 6952
• 5a Lübbe C, Dumrath A, Neumann H, Beller M, Kadyrov R. ChemCatChem 2014; 6: 105
• 5b Kadyrov R, Azap C, Weidlich S, Wolf D. Top. Catal. 2012; 55: 538
• 5c Kadyrov R, Rosiak A. Chemistry Today 2009; 27: 24

For reviews, see:
• 6a Jahnke MC, Hahn FE. In N-Heterocyclic Carbenes: From Laboratory Curiosities to Efficient Synthetic Tools . Diez-Gonzalez S. Royal Society of Chemistry; London: 2017: 1-41
• 6b Benhamou L, Chardon E, Lavigne G, Bellemin-Laponnaz S, Cesar V. Chem. Rev. 2011; 111: 2705
• 6c Zhong R, Lindhorst AC, Groche FJ, Kühn FE. Chem. Rev. 2017; 117: 1970

For selected references, see:
• 7a Herrmann WA, Goossen LJ, Artus GR. J, Köcher C. Organometallics 1997; 16: 2472
• 7b Arduengo AJ. III, Krafczyk R, Schmutzler R. Tetrahedron 1999; 55: 14523
• 7c Hirano K, Urban S, Wang C, Glorius F. Org. Lett. 2009; 11: 1019; and references cited therein
• 7d Lv T, Wang Z, You J, Lan J, Gao G. J. Org. Chem. 2013; 78: 5723
• 8a Schönherr H.-J, Wanzlick H.-W. Justus Liebigs Ann. Chem. 1970; 731: 176
• 8b Schönherr H.-J, Wanzlick H.-W. Chem. Ber. 1970; 103: 1037
• 8c Arduengo AJ. III, Goerlich JR, Krafczyk R, Marshall WJ. Angew. Chem. Int. Ed. 1998; 37: 1963; Angew. Chem. 1998, 110, 2062
• 8d Dowe AP, Li H, Pratt RC, Lohmeijer BG. G, Culkin DA, Waymouth RM, Hedrick JL. Chem. Commun. 2006; 2881
• 8e Ogle JW, Zhang J, Reibenspies JH, Abboud KA, Miller SA. Org. Lett. 2008; 10: 3677
• 8f Ogle JJ. W, Miller SA. Chem. Commun. 2009; 5728
• 8g Mehrotra KN, Singh G. Synthesis 1980; 1001
• 9a Schroeder DC. Chem. Rev. 1955; 55: 181
• 9b Azizi N, Khajeh-Amiri A, Ghafuri H, Bolourtchian M. Mol. Diversity 2011; 15: 157
• 9c Li Z, Liu D, Chen Y, Yin Y, Wang Z, Sun X. J. Chem. Res. 2016; 40: 515; and references cited therein
• 10 Sharma S. Synthesis 1978; 803
• 11a Dyson G, George HJ. J. Chem. Soc. 1924; 1702
• 11b Natarajan A, Guo Y, Arthanari H, Wagner G, Halperin JA, Chorev M. J. Org. Chem. 2005; 70: 6362
• 11c Štrukil V, Igrc MD, Fábián L, Eckert-Maksić M, Childs SL, Reid DG, Duer MJ, Halasz I, Mottilloe C, Friščić T. Green Chem. 2012; 14: 2462
• 12 Staab HA, Walther G. Justus Liebigs Ann. Chem. 1962; 657: 98
• 13a Ballabeni M, Ballini R, Bigi F, Maggi R, Parrini M, Predieri G, Sartori G. J. Org. Chem. 1999; 64: 1029
• 13b Venkatesh P, Pandeya SN. E-J. Chem. 2009; 6: 495
• 13c Maddani MR, Prabhu KR. J. Org. Chem. 2010; 75: 2327
• 14 Piel I, Pawelczyk MD, Hirano K, Fröhlich R, Glorius F. Eur. J. Org. Chem. 2011; 5475
• 15a Biltz H. Ber. Dtsch. Chem. Ges. 1907; 40: 4799
• 15b Klüpfel KW, Stumpf HR, Behmenburg H, Neugebauer W, Süß O, Tomanek M. German Patent Appl. DE 1060713, 1959 ; Chem. Abstr. 1961, 55, 20735b
• 16 Grimmett MR. In Science of Synthesis, Vol. 12. Neier R. Georg Thieme Verlag; Stuttgart: 2002
• 17 Pesch J, Harms K, Bach T. Eur. J. Org. Chem. 2004; 2025
• 18 Carpenter MS, Easter WM, Wood TF. J. Org. Chem. 1951; 16: 586
• 19 Dyson GM, George HJ, Hunter RF. J. Chem. Soc. 1927; 436
• 20 Pohloudek-Fabini R. Arch. Pharm. 1965; 298: 51
• 21 Strukil V, Gracin D, Magdysyuk OV, Dinnebier RE, Friscic T. Angew. Chem. Int. Ed. 2015; 54: 8440
• 22 Huebner CF, Marsh JL, Mizzoni RH, Mull RP, Schroeder DC, Troxell HA, Scholz CR. J. Am. Chem. Soc. 1953; 75: 2274
• 23 Pasha MA, Madhusudana Reddy MB. Synth. Commun. 2009; 39: 2928
• 24 Natarajan A, Guo Y, Arthanari H, Wagner G, Halperin JA, Chorev M. J. Org. Chem. 2005; 70: 6362
• 25 Lippert KM, Hof K, Gerbig D, Ley D, Hausmann H, Guenther S, Schreiner PR. Eur. J. Org. Chem. 2012; 5919
• 26 Kokorev GI, Yambushev FD. Zh. Obshch. Khim. 1987; 57: 1552
• 27 Deady LW, Ganame D, Hughes AB, Quazi NH, Zanatta SD. Aust. J. Chem. 2002; 55: 287
• 28 Katritzky AR, Witek RW, Rodriguez-Garcia V, Mohapatra PP, Rogers JW, Cusido J, Abdel-Fattah AA. A, Steel PJ. J. Org. Chem. 2005; 70: 7866
• 29 Yang D, Chen Y.-C, Zhu N.-Y. Org. Lett. 2004; 6: 1577
• 30 Findlater M, Hill NJ, Cowley AH. Dalton Trans. 2008; 4419
• 31 Walter W, Randau G. Justus Liebigs Ann. Chem. 1969; 722: 52