Corrigendum to “AlCl3-promoted reaction of cycloalkanones with hydrazones: A convenient direct synthesis of 4,5,6,7-tetrahydro-1H-indazoles and their analogues” (Tetrahedron Letters (2019) 60(35), (S0040403919307439), (10.1016/j.tetlet.2019.150988))

Article abstract of DOI:10.1016/j.tetlet.2019.151107

The authors regret that the printed version of the above article contained errors in Tables 1 and 2. A plausible mechanism was proposed using 1-benzylidene-2-phenylhydrazine 1a and cyclohexanone 2a as model reactants (Scheme 2). The formation of aluminum

Full text of DOI:10.1016/j.tetlet.2019.151107

Tetrahedron Letters 60 (2019) 151107
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Corrigendum to ‘‘AlCl3-promoted reaction of cycloalkanones with
hydrazones: A convenient direct synthesis of 4,5,6,7-tetrahydro-1H-
indazoles and their analogues” [Tetrahedron Lett. 60 (2019) 150988]
Rima Laroum a, Fabienne Berrée b, Thierry Roisnel b, Vincent Dorcet b, Bertrand Carboni b,
,
⇑
Abdelmadjid Debache a,
⇑
a Laboratoire de Synthèse des Molécules d’Intérêts Biologiques, Université des Frères Mentouri-Constantine, 25000 Constantine, Algeria
b Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes), UMR 6226, F-35000 Rennes, France
The authors regret that the printed version of the above article
contained errors in Tables 1 and 2. A plausible mechanism was
proposed using 1-benzylidene-2-phenylhydrazine 1a and cyclo-
hexanone 2a as model reactants (Scheme 2). The formation of
aluminum enolate 4 is followed by the addition of hydrazone to
afford hydrazinoketone 5 [24]. Cyclization provides the corre-
sponding 2,3,4,5,6,7-hexahydro-1H-indazole via the elimination
of water. The final aromatization step results from oxidation by
atmospheric oxygen, either during the reaction or upon workup
[13, 25]. This proposal is in agreement with the observed regiose-
lectivity in the case of b -tetralone 3af resulting from the more
stable enolate. Corrections are shown below. The authors would
like to sincerely apologise for any inconvenience caused.
DOI of original article: https://doi.org/10.1016/j.tetlet.2019.150988
Corresponding authors.
E-mail addresses: bertrand.carboni@univ-rennes1.fr (B. Carboni), a_debache@
⇑
yahoo.fr (A. Debache).
https://doi.org/10.1016/j.tetlet.2019.151107
0040-4039/Ó 2019 Elsevier Ltd. All rights reserved.

2
R. Laroum et al. / Tetrahedron Letters 60 (2019) 151107
Table 1
Table 2
Optimization of the reaction conditions.
Scope of the AlCl3-catalyzed reaction of alkanones with hydrazones.a,b
Entry
Acid
2a (equiv.)
Acid (equiv.)
Yield 3aa(%)a
1
2
3
4
5
6
7
8
AlCl3
FeCl3
Yb(OTf)3
PhB(OH)2
TosOH
AlCl3
1
1
1
1
1
1.5
1
1
1
0.1
1
1
2
2
2
49
45
35
0
0
72
53
45
AlCl3
AlCl3
2
a
Yield was calculated using the 1H NMR of the crude product with 1,3,5-
trimethoxybenzene as an internal standard.
a
Reagents and conditions: 1 (1 mmol), alkanone 2 (1.5 mmol), AlCl3, (2 mmol),
1,2-dichloroethane (5 mL), 80 °C, 16 h.
Isolated yields after purification by column chromatography.
b