- p-TSA-Based DESs as “Active Green Solvents” for Microwave Enhanced Cyclization of 2-Alkynyl-(hetero)-arylcarboxylates: an Alternative Access to 6-Substituted 3,4-Fused 2-Pyranones
-
In this paper, we describe the use of p-TSA based Deep Eutectic Solvents (DESs) as alternative environmental-friendly “active” solvents for the microwave-mediated synthesis of 6-substituted 3,4-fused 2-pyranones, and in particular isocoumarins, starting from 2-alkynyl-(hetero)arylcarboxylates. When the alkyne terminus bears a neutral or an electron-donating group (EDG), the reactions are fast, clean and highly regioselective, to give the 6-endo-dig cyclization products in good to excellent yields. For substrates bearing an electron-withdrawing group (EWG) on the alkyne end, the regioselectivity can be tuned by adding a small amount of silver(I) triflate as co-catalyst. DES was demonstrated to be reusable without loss of efficiency in terms of reaction yields. Based on experimental evidence and previous findings, two competitive mechanisms working simultaneously are proposed to explain the outcomes and the regioselectivity issues.
- Curti, Fabiola,Tiecco, Matteo,Pirovano, Valentina,Germani, Raimondo,Caselli, Alessandro,Rossi, Elisabetta,Abbiati, Giorgio
-
p. 1904 - 1914
(2019/02/26)
-
- Synthesis of isocoumarins: Rhenium complex-catalyzed cyclization of 2-ethynylbenzoic acids
-
When 2-ethynylbenzoic acids were treated with a catalytic amount of a rhenium complex, such as ReCl(CO)5, 6-endo cyclization of 2-ethynylbenzoic acids proceeded with a high selectivity to give the corresponding isocoumarins in moderate to good yields.
- Umeda, Rui,Yoshikawa, Shunya,Yamashita, Kouji,Nishiyama, Yutaka
-
p. 2172 - 2179
(2015/12/12)
-
- Directing the regioselectivity of rhodium(I) catalysed cyclisation of 2-alkynyl benzoic acids
-
Rhodium(I) dicarbonyl complexes 1-4 containing chelating N-donor ligands bis(pyrazolyl)methane (bpm), bis(imidazolyl)methane (bim), tris(pyrazolyl) toluidine (tpt) or tris(imidazolyl)methanol (tim) were investigated as catalysts for the hydroalkoxylation of alkynyl benzoic acids (5a-g). The regioselectivity of the reaction was shown to be highly dependent on the nature of the terminal alkyne substituent (R) of the alkynol substrate. It was also determined that the presence of a third uncoordinated N-donor group in complexes 3 and 4 suppressed the catalytic efficiency of these complexes, and that the selectivity of the reaction for forming either endocyclic (6) or exocyclic (7) hydroalkoxylation products was influenced by the pendant hydroxyl group present in complex 4. We used 13C NMR spectroscopy to quantify the polarity of the alkynyl benzoic acid C≡C bond and our efforts to correlate this measure of bond polarity to the observed regioselectivity of the reaction are discussed.
- Man, Bradley Y.-W.,Knuhtsen, Astrid,Page, Michael J.,Messerle, Barbara A.
-
p. 248 - 252
(2013/10/22)
-
- Microwave-promoted synthesis of some novel 4-(4-methyl-phenyl)-substituted phthalazin-1-one derivatives
-
In this study, a series of 4-(4-methyl-phenyl)-substituted phthalazin-1-one derivatives have been synthesized with the combination of rapid microwave synthesis and phasetransfer catalyst methodology, which is characterized by very short reaction times and easy workup procedures and which can be exploited to generate some novel phthalazinone heterocycles. Substituted phthalazin-1-one derivatives have been synthesized from phthalyl derivatives as starting material. The structures of these compounds were confirmed by NMR and mass spectral studies.
- Havaldar, Freddy H.,Dabholkar, Bhushan V.,Mule, Ganesh B.
-
p. 1127 - 1137
(2013/04/10)
-
- Catalytic enantioselective synthesis of chiral phthalides by efficient reductive cyclization of 2-acylarylcarboxylates under aqueous transfer hydrogenation conditions
-
A new diamine ligand for asymmetric transfer hydrogenation (ATH) was discovered. The reductive cyclization of 2-acylarylcarboxylates was found to proceed highly stereoselective by the new Ru complex-catalyzed ATH and subsequent In situ lactonization under aqueous conditions. It enables efficient access to a wide variety of 3-substituted phthalides In enantiomerically pure form.
- Zhang, Bo,Xu, Ming-Hua,Lin, Guo-Qiang
-
supporting information; experimental part
p. 4712 - 4715
(2009/12/08)
-
- The imidazo[2,1-a]isoindole system. A new skeletal basis for antiplasmodial compounds
-
The in vitro antiplasmodial activity of some dihydrostilbenamides, phtalazinones, imidazo[2,1-a]isoindole and pyrimido[2,1-a]isoindole derivatives related to the natural dihydrostilbenoid isonotholaenic acid is reported. The evaluation was performed on cultures of F32 strain of Plasmodium falciparum and potent representative compounds were also evaluated in the ferriprotoporphyrin IX biomineralization inhibition test (FBIT). Compounds having the imidazo[2,1-a]isoindole skeleton were the most active and one compound of this group resulted to be as potent as chloroquine, but acting through a mechanism different that of the inhibition of heme biomineralization.
- Del Olmo, Esther,Armas, Marlon Garcia,Ybarra, Ma. Ines,Lopez, Jose Luis,Oporto, Patricia,Gimenez, Alberto,Deharo, Eric,San Feliciano, Arturo
-
p. 2769 - 2772
(2007/10/03)
-
- Novel antiasthmatic agents with dual activities of thromboxane A2 synthetase inhibition and bronchodilation. 1. 2-[2-(1-imidazolyl)alkyl]- 1(2H)-phthalazinones
-
A number of 4-substituted 2-[ω-(1-imidazolyl)alkyl]-1(2H)-phthalazinones were synthesized in order to develop agents possessing both thromboxane A2 synthetase inhibitory and bronchodilatory activities. The pharmacological evaluation of these compounds disclosed that they have both activities to various extents. Both activities were slightly dependent on the length of the 2-substituents and largely affected by the nature of the 4-substituents. Compounds bearing phenyl and thienyl groups exhibited relatively high and well-rounded activities. Among these compounds, 12j and 15f were found to be the most effective agents having well-rounded activities in vitro and in vivo. Introduction of a carboxyl group reduced both activities contrary to our expectation. 4-(3-Pyridyl)phthalazinone 18b was of particular interest because of unexpectedly high in vivo activities in spite of an absence of significant in vitro activities.
- Yamaguchi,Kamei,Koga,Akima,Kuroki,Ohi
-
p. 4052 - 4060
(2007/10/02)
-
- Atropisomerism in o-Arylacetyl-N,N-dimethylbenzamides
-
A series of o-arylacetyl-N,N-dimethylbenzamides, 1-7, being studied as models for chain tautomers, differed markedly in their 1H NMR spectral properties, as a function of the substituents R1-R4.In the two cases where substituents were placed ortho to the amide group, the benzylic protons were anisochronous at ambient temperatures.Reported dynamic 1H NMR results are consistent with concomitant C-N and aryl-CO torsional processes.The 13C carbonyl shifts are compared with those of model compounds.
- Jones, Paul R.,Weisman, Gary R.,Baillargeon, Maurice J.,Gosink, Thomas A.
-
p. 3618 - 3620
(2007/10/02)
-
