The CeCl₃·7H₂O/NaI/SiO₂ System as an Efficient Promoter for the Friedel-Crafts Reaction of Indoles to Nitroalkenes under Solvent-Free Conditions

Abstract

The cheap, nontoxic and easy-to-handle CeCl₃×7H₂O/NaI Lewis acid promoter is optimal with regard to economic and ecological consideration and allows for useful applications in the synthesis of heterocyclic polyfunctionalized molecules. The procedure becomes efficient if the reaction is carried out under solvent-free conditions and on the surface of CeCl₃×7H₂O/NaI supported on silica gel. The simplicity of our method, especially that no precautions need to be taken to exclude moisture or oxygen from the reaction system, permit us to perform the Friedel-Crafts-type conjugate addition of indoles to nitroalkenes. The success of the reaction is independent of the type of indole or nitroalkene used, and provides 3-(2-nitroethyl)indolyl derivatives which are useful building blocks for the synthesis of various types of 3-(2-aminoethyl)indolyl derivatives. These can be subsequently transformed to the β-carbolines with different substituents.

Key words

addition reactions - alkaloids - heterocycles - indoles - lanthanides - Lewis acids - natural products

References

• 1 Olah GA. Krishnamurti AR. Prakash GKS. In Comprehensive Organic Synthesis   Vol. 3:  Trost BM. Fleming I. Pergamon Press; Oxford: 1999.  p.293-299  
• 2 Ninomiya I. J. Nat. Prod.  1992,  55:  541 
• 3a Zhang H. Larock RC. Org. Lett.  2001,  3:  3083 
• 3b Jiang B. Yang C.-G. Wang J. J. Org. Chem.  2001,  66:  4865 
• 3c Sakagami M. Muratake H. Natsume M. Chem. Pharm. Bull.  1994,  42:  1393 
• 3d Vaillancouirt V. Albizati KF. J. Am. Chem. Soc.  1993,  115:  3499 
• 4a Manabe K. Aoyama N. Kobayashi S. Adv. Synth. Catal.  2001,  343:  174 
• 4b Mori Y. Kakumoto K. Manabe K. Kobayashi S. Tetrahedron Lett.  2000,  41:  3107 
• 4c Manabe K. Mori Y. Wekabayashi T. Nagayama S. Kobayashi S. J. Am. Chem. Soc.  2000,  122:  7202 
• 6 Tundo P. Anastas P. Black DC. Breen J. Collins T. Memoli S. Miyamoto J. Polyakoff M. Tumas W. Pure Appl. Chem.  2000,  72:  1207 
• 7a Metzger JO. Angew. Chem. Int. Ed.  1998,  37:  2975 
• 7b Toda F. Tanaka K. Chem. Rev.  2000,  100:  1025 
• 8a Cornelis A. Laszlo P. Synthesis  1985,  909 
• 8b McKillop A. Young DW. Synthesis  1979,  401 
• 9a Bartoli G. Bosco M. Carlone A. Locatelli M. Marcantoni E. Melchiorre P. Sambri L. Adv. Synth. Catal.  2006,  348:  905 
• 9b Bartoli G. Bartolacci M. Giuliani A. Marcantoni E. Massaccesi M. Torregiani E. J. Org. Chem.  2005,  70:  169 
• 9c Bartoli G. Bosco M. Giuliani A. Marcantoni E. Palmieri A. Petrini M. Sambri L. J. Org. Chem.  2004,  69:  1290 
• 9d Bartoli G. Marcantoni E. Sambri L. Synlett  2003,  2101 ; and references cited therein
• 10a Bartoli G. Bosco M. Foglia G. Giuliani A. Marcantoni E. Sambri L. Synlett  2004,  895 
• 10b Bartoli G. Bartolacci M. Bosco M. Foglia G. Giuliani A. Marcantoni E. Sambri L. Torregiani E. J. Org. Chem.  2003,  68:  4594 
• 11a Bartoli G. Giovannini R. Giuliani A. Marcantoni E. Massaccesi M. Melchiorre P. Paoletti M. Sambri L. Eur. J. Org. Chem.  2006,  1472 
• 11b Attanasi OA. Favi G. Filippone P. Forzato C. Giorgi G. Morganti S. Nitti P. Pitacco G. Rizzato E. Spinelli D. Valentini E. Tetrahedron  2006,  62:  6420 
• 11c Sabitha G. Kiran Kuma Reddy GS. Bhaska Reddy K. Mallikarjun Reddy N. Yadav JS. Adv. Synth. Catal.  2004,  346:  921 
• 11d Yadav JS. Reddy BVS. Srinivas M. Padmavani B. Tetrahedron  2004,  60:  3261 
• 12 Bandini M. Melchiorre P. Melloni A. Umani-Ronchi A. Synthesis  2002,  1110 
• 13 Berner OM. Tedeschi L. Enders D. Eur. J. Org. Chem.  2002,  1877 
• 14 Rosini G. Ballini R. Synthesis  1988,  833 
• 15 Bartoli G. Bosco M. Giuli S. Giuliani A. Lucarelli L. Marcantoni E. Sambri L. Torregiani E. J. Org. Chem.  2005,  70:  1941 
• 16a Cacchi S. Fabrizi G. Parisi LM. Org. Lett.  2003,  5:  3843 
• 16b Wang H. Usui T. Osada H. Ganesan A. J. Med. Chem.  2000,  43:  1577 
• 16c Saxton JE. J. Nat. Prod. Rep.  1997,  559 
• 17 Yamamoto H. In Lewis Acid Reagents   Oxford University Press; New York: 1999. 
• 18 Ballini R. Clemente RR. Palmieri A. Petrini M. Adv. Synth. Catal.  2006,  348:  191 
• 19 Mahboobi S. Wiegrebe W. Popp A. J. Nat. Prod.  1999,  62:  577 
• 20 Towers GHN. Abramovski Z. J. Nat. Prod.  1983,  46:  572 
• 21 Mahboobi S. Popp A. Burgemeister T. Schollmeyer D. Tetrahedron: Asymmetry  1998,  9:  2369 
• 22 Busacca CA. Eriksson MC. Dong Y. Prokopowicz AS. Salvagno AM. Tschantz MA. J. Org. Chem.  1999,  64:  4564 
• 23 Zhou H. Liao X. Cook JM. Org. Lett.  2004,  6:  249 
• 24 Chandler M. Contoy R. Cooper AWJ. Lamont RB. Scicinski JJ. Smart JE. Storer R. Weir NG. Wilson RD. Wyatt PG. J. Chem. Soc., Perkin Trans. 1  1995,  1189 

5

Generally, triflates are rather expensive and their use in large-scale synthetic methodology is very limited.