Novel one-pot approach to 2-aminofuran derivatives via multicomponent reaction of 3-hydroxy-4H-pyran-4-ones, α-ketoaldehydes and methylene active nitriles

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton-Katritzky rearrangement

For the first time, the interaction of aroyl containing pyrano[2,3-d]isoxazolone derivatives with various hydrazines was studied. It was shown that the considered process includes formation of corresponding hydrazones followed by Boulton-Katritzky rearrangement. As a result, the general method for the synthesis of substituted 1,2,3-triazoles bearing an allomaltol fragment was elaborated. The suggested approach can be applied to various aromatic and heterocyclic hydrazines. At the same time for unsubstituted hydrazine the Boulton-Katritzky recyclization is not implemented. In this case the opening of the pyranone ring was observed leading to pyrazolylisoxazole derivatives. Both types of aforementioned structures were proved by X-ray analysis.

Aryl glyoxal: a prime synthetic equivalent for multicomponent reactions in the designing of oxygen heterocycles

The category of bifunctional building blocks overrides many others because of their fascinating wide applicability in synthetic chemistry. Aryl glyoxal is one of the key molecules that has been extensively used in heterocyclic chemistry to afford nearly all types of five- and six-membered heterocycles, which are the structural constituents of many natural products. The multicomponent reaction is a practical strategy to utilize this wonderful moiety with different types of starting materials to obtain numerous diverse oxygen heterocycles. This review covers the advancement of aryl glyoxal as a prime synthetic equivalent in recent years for the synthesis of oxygen heterocycles.

Supported l-tryptophan on Fe3O4@SiO2 as an efficient and magnetically separable catalyst for one-pot construction of spiro[indene-2,2'-naphthalene]-4'-carbonitrile derivatives

In this work, l-tryptophan functionalized silica-coated magnetic nanoparticles were readily prepared and evaluated as a recyclable magnetic nanocatalyst for the synthesis of spiro[indene-2,2'-naphthalene]-4'-carbonitrile derivatives through the one-pot four-component reaction of malononitrile, cyclohexanone, aromatic aldehydes, and 1,3-indandione. This novel magnetic nanocatalyst was confirmed to be effective and provide products in moderate to excellent yields under reflux conditions. The structure of obtained nanoparticles was characterized using FT-IR, XRD, VSM, EDX, elemental mapping, FE-SEM, and TGA. This synthetic protocol provides several benefits such as excellent yields in short reaction times (64-91%), saving costs, reusability of the catalyst using an external magnet (seven runs), and low catalyst loading.

Crystal structure of 3-allyl-4-(2-bromoethyl)-5-(4-methoxyphenyl)-2-(p-tolyl)furan, C23H23BrO2

C23H23BrO2, monoclinic, P21/c (no. 14), a = 24.193(4) Å, b = 5.8614(10) Å, c = 13.873(3) Å, β = 93.168(3)∘, V = 1964.3(6) Å3, Z = 4, R gt (F) = 0.0316, wR ref (F 2) = 0.0915, T = 296(2) K.

Crystal structure of 3-allyl-4-(2-bromoethyl)-5-(4-methoxyphenyl)-2-phenylfuran, C22H21BrO2

C21H21BrO2, monoclinic, P21/c (no. 14), a = 22.175(2) Å, b = 5.8375(6) Å, c = 14.8729(14) Å, β = 100.936(1)°, V = 1890.3(3) Å3, Z = 4, R gt (F) = 0.0343, wR ref(F 2) = 0.0839, T = 296(2) K.

Photoinduced assembly of the 3,4,4a,7a-tetrahydro-1H-cyclopenta[b]pyridine-2,7-dione core on the basis of allomaltol derivatives

A novel photochemical method for the construction of previously unknown substituted 4a,7a-dihydroxy-5-methyl-3,4,4a,7a-tetrahydro-1H-cyclopenta[b]pyridine-2,7-diones based on readily available allomaltol derivatives containing an amide group was established. The proposed approach includes the photoinduced contraction of an allomaltol ring and the subsequent intramolecular cyclization of an unstable α-hydroxy-1,2-diketone intermediate. For the first time we have shown the use of a side chain amide function as a trapping element for the final cyclization of photogenerated α-hydroxy-1,2-diketones. The structures of two synthesized photoproducts were determined by X-ray diffraction.

Construction of Spiro-γ-butyrolactone Core via Cascade Photochemical Reaction of 3-Hydroxypyran-4-one Derivatives

We elaborate a novel one-step photochemical method for the synthesis of spiro-γ-butyrolactone derivatives from 3-hydroxypyran-4-ones. The suggested approach is based on a cascade process including initial photoinduced contraction of 4-pyranone ring followed by intramolecular cyclization leading to the final spiro system. A distinctive feature of the proposed method is intramolecular trapping of unstable α-hydroxydiketone intermediate formed in situ as a result of a photochemical reaction. The structures of two synthesized 1-oxaspiro[4.4]non-8-ene-2,6,7-triones were determined by X-ray diffraction.