Abstract
A new organocatalytic procedure for the synthesis of bis(indolyl)methanes with acidic ionic liquid immobilized on silica gel (ILIS-SO2 Cl) has been developed. The reaction condition is applicable to a variety of aryl and aliphatic aldehydes and indoles. The mild nature of the reaction conditions showed that the acetoxy or TBDMS group in the aldehyde was maintained intact. The catalyst was reused four times in 93% average yield.
Key words
catalysis - condensation - indoles - ionic liquids - supported catalysis
References and Notes
1a Welton T.
Chem. Rev.
1999,
99:
2071
1b Rogers RD.
Seddon KR. In Ionic Liquids: Industrial Applications to Green Chemistry, ACS Symposium Series 818
Rogers RD.
Seddon KR.
American Chemical Society;
Washington D.C.:
2002.
1c Olivier-Bourbigou H.
Magna L.
J. Mol. Catal. A: Chem.
2002,
182-183:
419
1d Ionic Liquids in Synthesis
Wasserscheid P.
Welton T.
Wiley-VCH;
Weinheim:
2003.
1e Green Industrial Applications of Ionic Liquids
Rogers RD.
Seddon KR.
Kluwer;
Dordrecht:
2003.
2a Qiao K.
Yokoyama C.
Chem. Lett.
2004,
33:
472
2b Qiao K.
Yokoyama C.
Chem. Lett.
2004,
33:
808
2c Qiao K.
Deng Y.
Yokoyama C.
Sato H.
Yamashina M.
Chem. Lett.
2004,
33:
1350
3a Hagiwara H.
Inotsume S.
Fukushima M.
Hoshi T.
Suzuki T.
Chem. Lett.
2006,
35:
926
3b Hagiwara H.
Isobe K.
Numamae A.
Hoshi T.
Suzuki T.
Synlett
2006,
1601
3c Hagiwara H.
Numamae A.
Isobe K.
Hoshi T.
Suzuki T.
Heterocycles
2006,
68:
889 ; and earlier references cited therein
4 Qiao K.
Hagiwara H.
Yokoyama C.
J. Mol. Catal. A: Chem.
2006,
246:
65
5a Porter JK.
Bacon CW.
Robins JD.
Himmelsbach DS.
Higman HC.
J. Agric. Food Chem.
1977,
25:
88
5b Osawa T.
Namiki M.
Tetrahedron Lett.
1983,
24:
4719
5c Fahy E.
Potts BCM.
Faulkner DJ.
Smith K.
J. Nat. Prod.
1991,
54:
564
5d Bifulco G.
Bruno I.
Riccio R.
Lavayre J.
Bourdy G.
J. Nat. Prod.
1995,
58:
1254
5e Bell R.
Carmell S.
Sar N.
J. Nat. Prod.
1994,
57:
1587
5f Garbe TR.
Kobayashi M.
Shimizu N.
Takesue N.
Ozawa M.
Yukawa H.
J. Nat. Prod.
2000,
63:
596
6 Povszasz J.
Katakin GP.
Foleat S.
Malkovics B.
Acta Phys. Acad. Sci. Hung.
1996,
29:
299
7a Hong C.
Firestone GL.
Bjeldanes LF.
Biochem. Pharmacol.
2002,
63:
1085
7b Carter TH.
Liu CK.
Ralph W.
Chen D.
Qi M.
Fan S.
Yuan E.
Rosen EM.
Auborn KJ.
J. Nutr.
2002,
132:
3314
8a Nagarajan R.
Perumal PT.
Chem. Lett.
2004,
33:
288
8b Chakrabarty M.
Mukherji A.
Karmakar S.
Arims S.
Harigaya Y.
Heterocycles
2006,
68:
331
8c Chakrabarty M.
Mukherjee R.
Mukherji A.
Arims S.
Harigaya Y.
Heterocycles
2006,
68:
1659 ; and earlier references cited in these references
9a Ji S.-J.
Zhou M.-F.
Gu D.-G.
Wang S.-Y.
Loh T.-P.
Synlett
2003,
2077
9b Ji S.-J.
Zhou M.-F.
Gu D.-G.
Jiang Z.-Q.
Loh T.-P.
Eur. J. Org. Chem.
2004,
1584
10 Gu D.-G.
Ji S.-J.
Jiang Z.-Q.
Zhou M.-F.
Loh T.-P.
Synlett
2005,
959
11
Typical Experimental Procedure : A suspension of the benzaldehyde (1 ) (30 mL, 0.3 mmol), indole(2 ) (60 mg, 0.5 mmol) and ILIS-SO2 Cl(4 ) (143 mg, loading of sulfonyl chloride: 0.35 mmol/g, 0.05 mmol) in MeCN (3 mL) was stirred gently at ambient temperature under nitrogen atmosphere for 5.5 h. The product was triturated with Et2 O and the combined organic layer was evaporated to dryness. Medium pressure LC of the residue (eluent: EtOAc-n -hexane, 3:1) afforded bis(indolyl)methane(3 ) (79 mg, 97% based on 2 ).
12a Leach MR. In Lewis Acid/Base Reaction Chemistry
Meta-Synthesis;
Brighton UK:
1999.
12b According to preliminary MOPAC-AM1 calculation, LUMO energy of methanesulfonyl chloride was 4.1 eV lower than that of BF3 , though the shape of the LUMO was not localized.
