Abstract
A new synthetic route to afford 2-amino-5-aryl thiazoles has been developed. The starting aminothiazole derivative can be arylated at position 5 with aryl iodides under palladium-catalyzed conditions. Mechanistic studies suggest a proton-abstraction pathway for this transformation.
Key words
palladium - catalysis - cross-coupling - heterocycles - Heck reaction
References and Notes
1a Kalgutkar AS.
Crews BC.
Marnett L.
J. Biochem.
1996,
35:
9076
1b Dondoni A.
Comprehensive Chemistry II
Vol. 3:
Shinkai I.
Pergamon;
Glasgow:
1996.
p.373
1c Hutchinson I.
Stevens MFG.
Westwell AD.
Tetrahedron Lett.
2000,
41:
425
2a Schwander H. In Ullman’s Encyclopedia of Industrial Chemistry
Vol. A11:
VCH;
Weinheim:
1988.
p.279
2b Mori A.
Sekiguchi A.
Masui K.
Shimada T.
Horie M.
Osakada K.
Kawamoto M.
Ikeda T.
J. Am. Chem. Soc.
2003,
125:
1700
3a Dölling K.
Zaschke H.
Schubert H.
J. Prakt. Chem.
1979,
321:
643
3b See also ref. 2b.
4a Hassan J.
Sévignon M.
Gozzi C.
Schulz E.
Lemaire M.
Chem. Rev.
2002,
102:
1359
4b Anastasia L.
Negishi E. In
Handbook of Organopalladium Chemistry for Organic Synthesis
Negishi E.
Wiley;
New York:
2002.
p.311
5a Dyker G.
Angew. Chem. Int. Ed.
1999,
38:
1698
5b Miura M.
Nomura M.
Top. Curr. Chem.
2002,
219:
211
5c Wolfe JP.
Thomas JS.
Curr. Org. Chem.
2005,
9:
625
6a Manolova P.
Zhelyazkov L.
Vodenicharov R.
Farmatsiya
1980,
30:
9
6b Volmajer J.
Toplak R.
Bittner S.
Majcen Le Marechal A.
ARKIVOC
2003,
(xiv):
49
7a Pivsa-Art S.
Satoh T.
Awamura Y.
Miura M.
Nomura M.
Bull. Chem. Soc. Jpn.
1998,
71:
467
7b Yokooji A.
Okazawa T.
Satoh T.
Miura M.
Nomura M.
Tetrahedron
2003,
59:
5685
7c Masui K.
Mori A.
Okano K.
Takamura K.
Kinoshita M.
Ikeda T.
Org. Lett.
2004,
6:
2011
7d Parisien M.
Valette D.
Fagnou K.
J. Org. Chem.
2005,
70:
7578
7e Bellina F.
Cauteruccio S.
Rossi R.
Eur. J. Org. Chem.
2006,
1379
7f See also ref. 2b.
8 Alberico D.
Scott ME.
Lautens M.
Chem. Rev.
2007,
107:
174
9 The Pd-coupling reaction with free 2-aminothiazole provided the corresponding amination product.
10 Lower yields were obtained with bidentate phosphine ligands, such as XantPhos (4,5-bis-diphenylphosphanyl-9,9-dimethyl-9H -xanthene, 64%), BINAP (60%) or DPPF [1,1′-bis(diphenylphosphino)ferrocene, 58%].
11 Li W.
Nelson DP.
Jensen MS.
Hoerrner RS.
Javadi GJ.
Cai D.
Larsen RD.
Org. Lett.
2003,
5:
4835
12
Typical Experimental Procedure
2 (0.37 mmol), aryl iodide (0.55 mmol), Cs2 CO3 (0.239 g, 0.73 mmol), Pd(OAc)2 (0.004 g, 5 mol%, 0.02 mmol), ligand 7 (0.014 g, 10 mol%, 0.04 mmol) and DMF (2 mL, 0.2 M). The resulting mixture was stirred at 120 °C for 24 h under a nitrogen atmosphere. The mixture was then filtered through Celite and concentrated to dryness. The residue was purified first on silica gel (4:1 hexane-EtOAc) and then with an HLB cartridge [using NH4 HCO3 (pH 10) and MeCN as eluents]. Next, the compound was dissolved in CH2 CH2 (1 mL) and TFA in CH2 CH2 (25%, 1 mL) was added. The corresponding solution was shaken on an arm shaker overnight. After that, the mixture was concentrated to dryness, dissolved in MeOH, passed through an SCX-2 cartridge; two volumes of MeOH and two volumes of NH3 -MeOH (2 N) were eluted. The NH3 -MeOH washings were concentrated to dryness to afford the desired compound.4a ): white solid (73 mg, 80%). 1 H NMR (300 MHz, CDCl3 ): δ = 7.47-7.38 (m, 5 H), 5.48-5.39 (m, 2 H), 4.23 (q, J = 7.1 Hz, 2 H), 1.19 (t, J = 7.1 Hz, 3 H). 13 C NMR (75 MHz, CDCl3 ): δ = 163.91, 160.92, 135.83, 134.10, 129.81, 129.02, 127.62, 126.99, 59.99, 13.02.
13a Grigg R.
Sridharan V.
Stevenson P.
Sukirthalingam S.
Worakum T.
Tetrahedron
1990,
46:
4003
13b Hughes CC.
Trauner D.
Angew. Chem. Int. Ed.
2002,
41:
1569
13c Lautens M.
Fang Y.-Q.
Org. Lett.
2003,
5:
3679
13d Glover B.
Harvey KA.
Liu B.
Sharp MJ.
Tymoschenko M.
Org. Lett.
2003,
5:
301
14a Catellani M.
Chiusoli GP.
J. Organomet. Chem.
1992,
425:
151
14b Martín-Matute B.
Mateo C.
Cárdenas DJ.
Echavarren AM.
Chem. Eur. J.
2001,
7:
2341
14c Lane BS.
Sames D.
Org. Lett.
2004,
6:
2897
14d Lane BS.
Brown MA.
Sames D.
J. Am. Chem. Soc.
2005,
127:
8050
15 Park C.-H.
Ryabova V.
Seregin IV.
Sromek AW.
Gevorgyan V.
Org. Lett.
2004,
6:
1159
16 Vacek G.
Perry JK.
Langlois J.-M.
Chem. Phys. Lett.
1999,
310:
189
17a Lee C.
Parr RG.
Yang W.
Phys. Rev.
1988,
37:
B785
17b Becke AD.
J. Phys. Chem.
1993,
98:
5648
17c Stephens PJ.
Devlin FJ.
Chabalowski CF.
Frisch MJ.
J. Phys. Chem.
1994,
98:
11623
18 García-Cuadrado D.
Braga AA.
Maseras F.
Echavarren AM.
J. Am. Chem. Soc.
2006,
128:
1066
19a Lafrance M.
Rowley CN.
Woo TK.
Fagnou K.
J. Am. Chem. Soc.
2006,
128:
8754
19b Campeau L.-C.
Parisien M.
Leblanc M.
Fagnou K.
J. Am. Chem. Soc.
2004,
126:
9186
19c Parisien M.
Valette D.
Fagnou K.
J. Org. Chem.
2005,
70:
7578
19d Campeau L.-C.
Parisien M.
Jean A.
Fagnou K.
J. Am. Chem. Soc.
2006,
128:
581
20 Hennessy EJ.
Buchwald SL.
J. Am. Chem. Soc.
2003,
125:
12084
21a Goossen LJ.
Koley D.
Hermann HL.
Thiel W.
J. Am. Chem. Soc.
2005,
127:
11102
21b Braga AAC.
Morgon NH.
Ujaque G.
Maseras F.
J. Am. Chem. Soc.
2005,
127:
9298
21c Mota AJ.
Dedieu A.
Bour C.
Suffert J.
J. Am. Chem. Soc.
2005,
127:
7171
22a Pivsa-Art S.
Satoh T.
Awamura Y.
Miura M.
Nomura M.
Bull. Chem. Soc. Jpn.
1998,
71:
467
22b See also ref. 14c,d, 15.
