Abstract
A new facile entry to the synthesis of 1,3-bis(indol-3-yl)butane-1-ones
is presented. The procedure effectively utilizes a InBr3 /TMSCl
mixture (10 mol%) as a promoter for the chemoselective
Michael addition of variously functionalised indoles to α,β-unsaturated
indolyl ketones. The excellent yields and the mildness of the experimental
conditions guarantee a widespread applicability of the protocol
towards the construction of functionalised keto-bis(indolyl) compounds.
Key words
catalysis - enones - indium - indoles - Michael additions
References
<A NAME="RZ15302SS-1">1 </A>
Zhao S.
Liao X.
Cook JM.
Org.
Lett.
2002,
4:
687 ;
and references cited therein
<A NAME="RZ15302SS-2A">2a </A>
Faulkner DJ.
J. Nat. Prod. Rep.
2001,
18:
1
<A NAME="RZ15302SS-2B">2b </A>
Miyake FY.
Yakushijin K.
Horne DA.
Org. Lett.
2002,
4:
941
<A NAME="RZ15302SS-2C">2c </A>
Jiang B.
Yang C.-G.
Wang J.
J.
Org. Chem.
2002,
67:
1396
<A NAME="RZ15302SS-3">3 </A>
Nenaidenko VG.
Baraznenok IL.
Balenkova FS.
Russ. J. Org. Chem.
1998,
34:
1019
<A NAME="RZ15302SS-4A">4a </A>
Bandini M.
Cozzi PG.
Giacomini M.
Melchiorre P.
Umani-Ronchi A.
J. Org. Chem.
2002,
67:
3700
<A NAME="RZ15302SS-4B">4b </A>
Bandini M.
Melchiorre P.
Melloni A.
Umani-Ronchi A.
Synthesis
2002,
1110
<A NAME="RZ15302SS-5">5 </A>
Okuachi T.
Itonaga M.
Minami T.
Owa T.
Kitoh K.
Yoshino H.
Org. Lett.
2000,
2:
1485
The combined use of chlorosilanes
and InCl3 as Lewis acids in organic transformations was
first reported by Mukaiyama et al.:
<A NAME="RZ15302SS-6A">6a </A>
Mukaiyama T.
Ohno T.
Han JS.
Kobayashi S.
Chem. Lett.
1991,
949
<A NAME="RZ15302SS-6B">6b </A>
Mukaiyama T.
Ohno T.
Nishimura T.
Han SJ.
Kobayashi S.
Bull.
Chem. Soc. Jpn.
1991,
64:
2524
For a discussion concerning the
accelerating effects of trimethylsilyl halides in catalyzed conjugate
additions, see:
<A NAME="RZ15302SS-7A">7a </A>
Corey EJ.
Boaz NW.
Tetrahedron
Lett.
1985,
26:
6015
<A NAME="RZ15302SS-7B">7b </A>
Corey EJ.
Boaz NW.
Tetrahedron
Lett.
1985,
26:
6019
<A NAME="RZ15302SS-7C">7c </A>
Pollock P.
Dambacher J.
Annes R.
Brgdahl M.
Tetrahedron Lett.
2002,
43:
3639
<A NAME="RZ15302SS-8">8 </A>
Benzothiophene and N -methylpyrrole
were also reacted with 1a in the presence
of InBr3 /TMSCl (10 mol%) affording
the corresponding 1,4-adduct in 18% and 72% yields, respectively.
With N -methylpyrrole, the product was isolated
as a 1:1 mixture of C-2/C-3 nucleophilic addition.
<A NAME="RZ15302SS-9A">9a </A>
Routier S.
Saugé L.
Ayerbe N.
Couder G.
Mérour J.-Y.
Tetrahedron Lett.
2002,
43:
589
<A NAME="RZ15302SS-9B">9b </A>
Nettekoven M.
Psiorz M.
Waldmann H.
Tetrahedron
Lett.
1995,
36:
1425
<A NAME="RZ15302SS-10">10 </A> A large excess of TMSCl was already
found helpful in promoting the Sakurai reaction in combination with
catalytic InCl3 :
Lee PH.
Lee K.
Sung S.
Chang S.
J. Org. Chem.
2001,
66:
8646
<A NAME="RZ15302SS-11">11 </A>
No Lewis acid/Lewis base
interaction was detectable by 1 H NMR (CD2 Cl2 ,
r.t.) analysis of a 1a /TMSCl mixture.
<A NAME="RZ15302SS-12">12 </A>
Bandini M.
Cozzi PG.
Garelli A.
Melchiorre P.
Umani-Ronchi A.
Eur.
J. Org. Chem.
2002,
3243
<A NAME="RZ15302SS-13">13 </A>
Onishi Y.
Iko T.
Yasuda M.
Baba A.
Tetrahedron
2002,
58:
8227
<A NAME="RZ15302SS-14A">14a </A>
de Koning CB.
Michael JP.
Rousseau AL.
J. Chem.
Soc., Perkin Trans. 1
2000,
1705
<A NAME="RZ15302SS-14B">14b </A>
Vaillancourt V.
Albizati KF.
J. Am. Chem. Soc.
1993,
115:
3499
<A NAME="RZ15302SS-14C">14c </A>
Mahboobi S.
Teller S.
Pongratz H.
Hufsky H.
Sellmer A.
Botzki A.
Uecker A.
Beckers T.
Baasner S.
Schächtele A.
Überall F.
Kassack MU.
Dove S.
Böhmer F.
J.
Med. Chem.
2002,
45:
1200