Substituted 2- arylfurans

The furan ring undergoes arylation with diazo compounds, but the yield is poor. Thus, furfural,23 2-furoic acid,158 and furylacrylic acid can be converted into 5-substituted arylfuran derivatives by diazo-nium salts (see further references in Ref. 159) ... 

The reactions of substituted furo[3,2- ]pyrrole-5-carbohydrazides with 5-arylfuran-2-carbaldehydes, 4,5-disubsti-tuted furan-2-carbaldehydes, and thiophene-2-carbaldehyde have been studied <2005CEC622>. The advantage of microwave (MW) irradiation on some of these reactions was reflected in the reduced reaction time and increased yields (Table 8). The series of substituted hydrazones 241-246 was obtained from these... 

Monobromination of 2-arylfurans para-substituted by halogen or nitro gave high yields (75-84%) of 5-bromo products two molar equivalents of bromine led to 3,5-dibromination (77-96%). Presumably there is better charge delocalization for 3- than for 4-substitution (80CHE334). Ethyl 5-bromo-2-furoate has been made by a bromodesilylation process (91MI1). 

Thermal decomposition to a dihalogenocarbene from an organomercury precursor in the presence of substituted benzaldehydes and dimethyl acetylene dicarboxylate produces 2-halogeno-5-arylfuran-3,4-dicarboxylates 292 in isolated yields that range from 13 to 64%. These products appear to be the... 

Arylfurans substituted in the 2 - and 4 -position react with DMAD in the presence of a Lewis acid to afford Diels-Alder adducts in good yields. A subsequent spontaneous or acid-induced P-elimination leads to polysubstituted phenylphenols <978631>. In a similar manner... 

ZOK632), arylfurans and arylthiophenes (66HCA1794), 2-arylbenzo-triazoles (92JA964), 2-(l-pyrrolyl, diazolyl, and for triazolyl)-substituted 5-nitropyridines with nonlinear optical properties (94BCJ1936). 

Base-assisted cyclization of l-[3-[hydroxy(substituted methyl)]propargyl]benzotriazoles, which are available from lithiated 1-propargylbenzotriazole and aromatic aldehydes, gives 2-arylfurans (Equation (13)) <93JOC3038>. 

The tosyloxylation of suitable ketones followed by heterocyclization has been utilized in the syntheses of the following heterocyclic systems 2-aroylbenzo[fe]furans [194], 3-aryl-5,6-dihydroimidazo[2,l- ][l,3]-thiazoles [194], 6-arylimidazo[2,l- ]thiazoles [195], (15 ,2/ )-indene oxide [196], 2-mercaptothiazoles [197], triazolo-[3,4-fc]-l,3,4-thiadiazines [198], dihydroindeno[l,2-e][l,2,4]triazolo[3,4- ][l,3,4]thiadiazines [199], furo[3,2-c]coumarins [200], 4,5-diarylisoxazoles [201], 2-substituted 4,5-diphenyloxazoles [202], quinoxaline [203], 3-carbomethoxy-4-arylfuran-2-(5//)-ones [204], thiazol-2(3//)-imine-linked glycoconju-gates [205] and other important heterocycles. 

Daugulis also showed that these conditions are suitable for C2-arylation of furans 7 with (hetero)aryl chlorides (Scheme 2) (2011JOC471). Substituted 2-(hetero)arylfurans 8 were acquired via 9 in moderate to good yield after 24 h reaction time. 

Preparation of5-Substituted-2-Furaldehydes 69 Table 3.24 Pd-catalyzed synthesis of 2-(5-arylfuran-2-yl)1,3-dioxolanes. 

Cyclopropylalkynes (27) readily react with hexacarbonylchromium to produce (3-cyclopropylpropynylidine)pentacarbonylchromium complexes (28) whose dimethyl-amine Michael adducts (29) undergo 3 -I- 2-cycloaddition with alkynes to yield cyclopropyl-substituted 3-ethoxy-5-dimethylaminocyclopentadienes (30) in very good yields (Scheme 11). A one-step synthesis of 2-arylfurans involves the cerium ammonium nitrate-mediated oxidative cycloaddition of cyclic and acyclic 1,3-dicarbonyl compounds to alkynes.The new chiral Ai-(ethynyl)allylglycines (31)... 

Gupton and coworkers developed a six-step stereoselective synthesis of N-substituted 5-benzyhdene-4-arylpyrrol-2-ones (2010T9113). Within this sequence, Gupton treated a variety of (Z)-5-benzyUdene-4-arylfuran-2-ones with alkyl- and arylamines in methylene chloride at room temperature to afford corresponding 5-benzyl-5-hydroxy-4-arylpytrol-2-ones. 

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