Categories: Synthesis of N-Heterocycles >
Synthesis of indoles
Name Reactions
Recent Literature
Gold(III)-catalyzed annulation of 2-alkynylanilines in EtOH or
EtOH-water mixtures at room temperature gives indoles derivatives in good
yields. One-flask protocol for the gold-catalyzed conversion of
2-alkynylanilines to 3-bromo and 3-iodoindoles is also reported.
A. Arcadi, G. Bianchi, F. Marinelli, Synthesis, 2004,
610-618.
Cross-coupling of 1-alkynes with vinyl iodides catalyzed by CuI/N,N-dimethylglycine
affords conjugated enynes in good to excellent yields. Heating a mixture of
2-bromotrifluoroacetanilide, 1-alkyne in the presence of CuI/L-proline
leads to the formation of the corresponding indole.
F. Liu, D. Ma, J. Org. Chem., 2007,
72, 4844-4850.
A copper(II)-catalyzed cyclization of 2-ethynylaniline derivatives to indoles
can be carried out in a mixture of H2O and MeOH in the presence of
1-ethylpiperidine at room temperature. A catalyst recycling reaction system was
established.
K. Hiroya, S. Itoh, T. Sakamoto, Tetrahedron, 2005,
61, 10958-10964.
Central to an alternative source of substrates for Fischer indolizations was a
palladium-catalyzed coupling to prepare N-aryl benzophenone hydrazones.
Hydrolysis of the hydrazones in the presence of ketones produced enolizable
hydrazones that underwent Fischer indolization.
S. Wagaw, B. H. Yang, S. L. Buchwald, J. Am. Chem. Soc., 1998,
120, 6621-6622
A three-component synthesis of substituted indoles starts from ortho-dihaloarenes
through the use of a multicatalytic system consisting of an N-heterocyclic
carbene palladium complex and CuI. Indole derivatives are obtained as single
regioisomers in high yields.
L. T. Kaspar, L. Ackermann, Tetrahedron, 2005,
61, 11311-11316.
Treatment of o-bromonitrobenzenes with various vinyl Grignard reagents
gives 7-bromoindoles in good yields, using the o-bromine atom to direct
the cyclization. A subsequent reduction using a heteroaryl radical methodology gives
7-unsubstituted indoles in nearly quantitative yields.
A. Dobbs, J. Org. Chem., 2001, 66,
638-641.
A new, mild, and efficient method for the synthesis of polyfunctionalized
indoles by direct reaction of substituted 2-chloroanilines with cyclic or
acyclic ketones was developed. This procedure is simple to carry out and
broadly applicable.
M. Nazare, C. Schneider, A. Lindenschmidt, D. W. Will, Angew. Chem. Int. Ed.,
2004, 43, 4526-4528.
One-pot synthesis of indoles by a palladium-catalyzed annulation of ortho-iodoanilines
and aldehydes is realized under mild ligandless conditions, whereas X-Phos
is found to be the ligand of choice for coupling reactions involving ortho-chloroanilines/ortho-bromoanilines and aldehydes.
Y. Jia, J. Zhu, J. Org. Chem., 2006, 71, 7826-7834.
A new palladium-catalyzed route to N-functionalized indoles has been developed in
which the N fragments are introduced in a single-step cascade sequence onto a
acyclic carbon framework.
M. C. Willis, G. N. Brace, I. P. Holmes, Angew. Chem. Int. Ed., 2005,
44, 403-406.
The Pd-catalyzed tandem C-N/Suzuki-Miyaura
coupling of readily prepared ortho-gem-dihalovinylanilines with boronic acids, esters, alkyl 9-BBN derivatives,
and trialkylboranes gave 2-substituted indoles in good to excellent yields. Optimal conditions
used low loadings of a Pd(OAc)2/S-Phos catalyst in the presence of K3PO4·H2O.
Y.-Q. Fang, M. Lautens, Org. Lett., 2005, 7, 3549-3552.
The solid-state reaction between anilines and phenacyl bromides in the presence
of an equimolecular amount of sodium bicarbonate or a second equivalent of the
aniline followod by microwave irradiation provides a mild, general, and
environmentally friendly method for the synthesis of 2-arylindoles in good
overall yields.
V. Sridharan, S. Perumal, C. Avendaño, J. C. Menéndez, Synlett,
2006, 91-95.
V. Sridharan, S. Perumal, C. Avendaño, J. C. Menéndez, Synlett,
2006, 91-95.
Rhodium(II) perfluorobutyrate-mediated decomposition of vinyl azides allows
rapid access to a variety of complex, functionalized N-heterocycles in
two steps from commercially available starting materials.
B. J. Stokes, H. Dong, B. E. Leslie, A. L. Pumphrey, T. G. Driver, J. Am. Chem. Soc., 2007,
129, 7500-7501.
Various N-arylated and N-alkylated indoles and pyrrole-fused aromatic compounds
were synthesized by a phenyliodine bis(trifluoroacetate) (PIFA)-mediated
intramolecular cyclization.
Y. Du, R. Liu, G. Linn, K. Zhao, Org. Lett., 2006,
8, 5919-5922.
A novel one-step synthesis of valuable 2-vinylic indoles and their tricycle
derivatives occurs via an efficient Pd-catalyzed tandem Buchwald-Hartwig/Heck
reaction using a gem-dibromovinyl unit as a readily available
starting material.
A. Fayol, Y.-Q. Fang, M. Lautens, Org. Lett.,
2006, 8, 4203-4206.
A practical one-pot, regiospecific three-component process for the synthesis
of 2,3-disubstituted indoles based on Cacchi's protocol was developed. This mild
Pd-catalyzed domino indolization procedure allows rapid access to various
indoles via consecutive
Sonogashira coupling, amidopalladation, and reductive elimination.
B. Z. Lu, W. Zhao, H.-X. Wei, M. Dufour, V. Farina, C. H. Senanayake, Org. Lett.,
2006, 8, 3271-3274.
The synthesis of a series of indole and carbazole derivatives from
2-fluorophenyl imines is reported. 2-Fluoroaniline-d4 is prepared
and used to investigate the mechanism of this indolization.
L. V. Kudzma, Synthesis, 2003, 1661-1666.
An effective reductive alkylation of electron-deficient o-chloroarylamines
was developed. The derived N-alkylated o-chloroarylamines were
elaborated to N-alkylazaindoles and N-alkylindoles via a novel
one-pot process comprising copper-free Sonogashira alkynylation and a
base-mediated indolization reaction.
M. McLaughlin, M. Palucki, I. W. Davies, Org. Lett.,
2006, 8, 3307-3310.
The reaction of Boc-protected ortho-aminostyrenes with alkyllithiums,
followed by the addition of specific electrophiles sets up a cascade
reaction process between the reacted electrophile and the ortho-amino
substituent, facilitating an in situ ring closure and dehydration to
generate an indole ring system.
C. M. Coleman, D. F. O'Shea, J. Am. Chem. Soc., 2003, 125, 4054-4055.
C. M. Coleman, D. F. O'Shea, J. Am. Chem. Soc., 2003, 125, 4054-4055.
Y.-Q. Fang, M. Lautens, Org. Lett., 2005, 7, 3549-3552.
[RuCl2(CO)3]2/dppp is a highly effective
catalyst system for the intramolecular oxidative amination of various
aminoalkenes in presence of K2CO3 and allyl acetate in
N-methylpiperidine to give the corresponding cyclic imines and
indoles in excellent yields.
T. Kondo, T. Okada, T.-A. Mitsudo, J. Am. Chem. Soc., 2002, 124,
186-187.
Zn(OTf)2 catalyzed the cyclization of propargyl alcohols with
anilines and phenols in toluene at 100°C without additive and gave various
indole and benzofuran products with different structures. The cyclization of
propargyl alcohols and amides gave oxazoles. Mechanisms for the different
substituation patterns are discussed.
M. P. Kumar, R.-S. Liu, J. Org. Chem., 2006, 71, 4951-4955.
Various 3-iodoindoles have been prepared in excellent yields by a
Sonogashira coupling of terminal
acetylenes with N,N-dialkyl-o-iodoanilines,
followed by an electrophilic cyclization of the resulting N,N-dialkyl-o-(1-alkynyl)anilines
using I2 in CH2Cl2. The reactivity of the carbon-nitrogen bond cleavage during cyclization follows: Me >
n-Bu, Me > Ph, and cyclohexyl > Me.
D. Yue, T. Yao, R. C. Larock, J. Org. Chem.,
2006, 71, 62-69.
A reverse aromatic Cope rearrangement of 2-allyl-3-alkylideneindolines obtained
by Horner-Wadsworth-Emmons olefination of 2-allylindolin-3-ones with diethyl
cyanomethylphosphonate provided α-allyl-3-indole acetonitriles. When
2-allylindolin-3-ones were treated with phosphonium ylides in refluxing toluene,
domino Wittig reaction and reverse aromatic Cope rearrangement took place to
give α-allyl-3-indole acetate derivatives in good yields.
T. Kawasaki, Y. Nonaka, K. Watanabe, A. Ogawa, K.
Higuchi, R. Terashima, K. Masuda, M. Sakamoto, J. Org. Chem., 2001, 66, 1200-1204.
| Related:
|
 |
Novel Synthetic Approaches Toward Substituted Indole Scaffolds |
