A concise method to synthesize 1-substituted 4-amino-2-(trifluoromethyl)-1H-pyrroles from the heterocyclization reaction of 5-bromo-4-methoxy-1,1,1-trifluoropent-3-en-2-ones with amines is described. This method has the following advantages: it uses a wide range of primary amines, starting materials are easily available, it is simple to perform, the reaction conditions are mild, it is environmentally friendly, and it furnishes yields of up to 98%.
5‐Bromo‐1,1,1‐trifluoro‐4‐methoxypent‐3‐en‐2‐one was used as an efficient precursor for the synthesis of a new series of (1,2,3‐triazol‐1‐yl)methyl‐pyrimidine biheterocycles. For this stepwise synthesis, the 5‐bromo‐1,1,1‐trifluoro‐4‐methoxypent‐3‐en‐2‐one was first converted into 5‐azido‐1,1,1‐trifluoro‐4‐methoxypent‐3‐en‐2‐one through a nucleophilic substitution of the bromine by an azide group. This was then followed by an azide–alkyne cycloaddition reaction (click chemistry) to give the key intermediate 5‐[4‐alkyl(aryl)‐1H‐1,2,3‐triazol‐1‐yl]‐1,1,1‐trifluoro‐4‐methoxypent‐3‐en‐2‐ones. These were cyclocondensed with 2‐methylisothiourea sulfate to give a series of 2‐(methylthio)‐4‐(1,2,3‐triazol‐1‐yl)methyl‐6‐(trifluoromethyl)pyrimidines. Additionally, the 2‐methylthiopyrimidine products were used to prepare a new series of 2‐amino‐4‐(1,2,3‐triazol‐1‐yl)methyl‐6‐(trifluoromethyl)pyrimidines.
The intramolecular electrophilic cyclization of 3-organoselanyl-2-alkynylindoles providing the synthesis of 3-iodo-selenophene-fused indoles is reported herein. The strategy was extended to the preparation of 3-iodo-thiophene-fused indoles in a one-pot iodine-promoted thiolation of 2-alkynylindoles, followed by an electrophilic cyclization sequence. Besides, the synthesis of 3-butylselanyl-selenophene-fused indoles from 3butylselanyl-2-alkynylindoles was also developed using iron(III) chloride and dibutyl diselenide to promote the cyclization and functionalization of the heterocycle. The identification of the alkyl halide intermediate afforded evidence to the proposed mechanism, which indicated that the reactions proceed through the formation of an iodonium ion, followed by a selenium 5-endo-dig cyclization, to afford the indole derivatives. The 3-iodo-selenonophene-fused indoles prepared were applied as substrates in copper-catalyzed crosscoupling reactions with thiols to give the Ullmann type products in good yields. Scheme 2. General strategy for the preparation of 3-organoselanyl-2-alkynylindoles. Scheme 3. 3-Organoselanyl-2-alkynylindoles prepared.
A method for the synthesis of 4-organoselanyl oxazinoindolone derivatives by the cascade cyclization of N-(alkoxycarbonyl)-2-alkynylindoles using iron(III) chloride and diorganyl diselenides as promoters was developed. This protocol was applied to a series of N-(alkoxycarbonyl)-2alkynylindoles containing different substituents. The reaction conditions also tolerated a variety of diorganyl diselenides having both electron donating and electron withdrawing groups. However, the reaction did not work for diorganyl disulfides and ditellurides. The reaction mechanism seems to proceed via an ionic pathway and the cooperative action between iron(III) chloride and diorganyl diselenides is crucial for successful cyclization. We also found that using the same starting materials, by simply changing the electrophilic source to iodine, led to the formation of 4-iodo-oxazinoindolones. The high reactivity of Csp 2 À Se and Csp 2 À I bonds were tested under cross-coupling conditions leading to the preparation of a new class of functionalized indole derivatives. In addition, the absorption, emission and electrochemical properties of 4organoselanyl oxazinoindolones showed an important relationship with the substituents of the aromatic rings. The advantages of the methodology include the use of electrophilic to promote the cyclization reaction and functionalization of the indole ring, and the electronic properties presented by the prepared compounds can be exploited as probes, analyte detectors and optical materials.
Chemoselective Synthesis of 1-Substituted 4-Amino-2-(trifluoromethyl)--1H-pyrroles Through the Heterocyclization Reaction of 4-Methoxy-5-bromo--1,1,1-trifluoropent-3-en-2-ones with Amines. -(AQUINO, E. D. C.; LEONEL, G.; GARIBOTI, V. C.; FRIZZO, C. P.; MARTINS, M. A. P.; BONACORSO, H. G.; ZANATTA*, N.; J. Org. Chem. 80 (2015) 24, 12453-12459, http://dx.
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