Useful, regioflexible methods for functionalization of 1-phenylpyrrole derivatives

Faigl, Ferenc; Mátravölgyi, Béla; Deák, Szilvia; Holczbauer, Tamás; Czugler, Mátyás; Balázs, László; Hermecz, István

doi:10.1016/j.tet.2012.03.070

Cited by 8 publications

(6 citation statements)

References 16 publications

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“…Regiose-lective monohalogenation of the -position of the pyrrole ring was finally accomplished by applying the mild conditions developed by our laboratory for the halogenation of 1-phenyl-1Hpyrrole derivatives. [19] It should be pointed out that 2,7-dihalofluorazone derivatives such as 5a,b have never been reported previously in the literature, and that in this case they could be accessed as a result of the selectivity of the monohalogenation protocol.…”

Section: Synthesis Of Compounds Ht157 and Ta1314mentioning

confidence: 91%

Synthesis and Investigation of Solar‐Cell Photosensitizers Having a Fluorazone Backbone

et al. 2017

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A synthetic sequence for the preparation of fully conjugated 2,7-disubstituted fluorazone (9H-pyrrolo[1,2--a]indol-9-one) derivatives has been developed comprising an Elming–Clauson–Kaas-type pyrrole formation, POCl3-mediated ring closure, selective halogenation and elongation of the conjugated backbone through cross-coupling reactions. As a proof of principle, this methodology was used to prepare for the first time two organic D–π–A dyes containing the fluorazone moiety. The new compounds display broad absorption bands in the visible-light region when adsorbed on nanocrystalline TiO2 and electrochemical properties compatible with their employment as photosensitizers in dye-sensitized solar cells. Small-scale photovoltaic devices fabricated with the fluorazone dyes yielded power conversion efficiencies in the range of 2.1–2.4 %, which correspond to approximately 70 % of the efficiency obtained with the reference organic dye DF15 under the same conditions

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Section: Synthesis Of Compounds Ht157 and Ta1314mentioning

confidence: 91%

Synthesis and Investigation of Solar‐Cell Photosensitizers Having a Fluorazone Backbone

et al. 2017

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“…Both the direct double metalation of substituted 1-phenylpyrroles followed by reaction with N , N -dimethylcarbamate carbonylating agent and Pd-catalyzed cyclocarbonylation are restricted to the synthesis of specific regioisomers of substituted fluorazones, due to the directing effects of functional groups . In addition, the preparation of the corresponding bromo or iodo derivatives applicable in cross-coupling reactions is unfeasible via these organometallic approaches, as halogen–metal exchange can occur during these transformations. , …”

Section: Introductionmentioning

confidence: 99%

Access to Fluorazones by Intramolecular Dehydrative Cyclization of Aromatic Tertiary Amides: A Synthetic and Mechanistic Study

et al. 2018

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An efficient synthesis has been developed for the preparation of 9H-pyrrolo[1,2-a]indol-9-ones (fluorazones) from readily available anthranilic acid derivatives via a one-pot amide- and pyrrole-formation step, followed by an intramolecular cyclodehydration. The cyclodehydration process is mediated by the activation of aromatic tertiary amides by triflic anhydride (TfO). Comparison of various benzo-substituents is shown to demonstrate the high functional group tolerance of this transformation. In addition, study of the reaction mechanism is also presented to unfold the exact role of the applied base additive. Herein, as a first example, we report our findings that TfO-mediated amide activation is obstructed by the easy protonation of amides by the formed triflic acid during the activation step. Additionally, it has been also proven that the base additive is not involved in the transformation of O-triflyliminium triflates into reactive species (e.g., nitrilium triflates) and is only responsible to neutralize the superacid to avoid the protonation of both the secondary or tertiary amides.

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“…In contrast, monolithiation at the 2 position is noted by using (i) the same base in diethyl ether at room temperature and long reaction times or in refluxing hexane (thermodynamic conditions) [ 11 – 12 ] or (ii) with butyllithium activated by potassium tert -butoxide (LICKOR) in tetrahydrofuran (THF) at −75 °C [ 11 , 13 ]. N -Arylpyrroles substituted on their six-membered ring by methoxy [ 14 ], halogen [ 15 – 16 ], alkyl [ 17 – 18 ], or trifluoromethyl [ 19 – 20 ] groups have been the topic of more recent studies. The reactions are in general performed at low temperatures (between −75 and 0 °C) and do not tolerate the presence of reactive functional groups.…”

Section: Introductionmentioning

confidence: 99%

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium–zinc base and regioselectivity-computed CH acidity relationship

Messaoud¹,

Bentabed‐Ababsa²,

Hedidi³

et al. 2015

Beilstein J. Org. Chem.

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SummaryThe synthesis of N-arylated pyrroles and indoles is documented, as well as their functionalization by deprotonative metallation using the base in situ prepared from LiTMP and ZnCl2·TMEDA (1/3 equiv). With N-phenylpyrrole and -indole, the reactions were carried out in hexane containing TMEDA which regioselectively afforded the 2-iodo derivatives after subsequent iodolysis. With pyrroles and indoles bearing N-substituents such as 2-thienyl, 3-pyridyl, 4-methoxyphenyl and 4-bromophenyl, the reactions all took place on the substituent, at the position either adjacent to the heteroatom (S, N) or ortho to the heteroatom-containing substituent (OMe, Br). The CH acidities of the substrates were determined in THF solution using the DFT B3LYP method in order to rationalize the experimental results.

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Useful, regioflexible methods for functionalization of 1-phenylpyrrole derivatives

Cited by 8 publications

References 16 publications

Synthesis and Investigation of Solar‐Cell Photosensitizers Having a Fluorazone Backbone

Synthesis and Investigation of Solar‐Cell Photosensitizers Having a Fluorazone Backbone

Access to Fluorazones by Intramolecular Dehydrative Cyclization of Aromatic Tertiary Amides: A Synthetic and Mechanistic Study

Deproto-metallation of N-arylated pyrroles and indoles using a mixed lithium–zinc base and regioselectivity-computed CH acidity relationship

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