Synthesis of 2,3-dihydrospiro[benzofuran-2,4′ -piperidines] and 2,3-dihydrospiro[benzofuran-2,3′-pyrrolidines]

The synthesis of 2,3-dihydrospiro[benzofuran-2,4′-piperidines] 3 and 2,3-dihydrospiro[benzofuran-2,3′]-pyrrolidine] 6 is described. The synthesis was achieved by a Grignard reaction of a 2-fluorobenzylhalide with an appropriate cycloazaalkyl ketone to yield the tertiary alcohols 1 and 4 . Subsequent intramolecular displacement of the aromatic fluoride by the derived alkoxides provided the novel system. Nitration of 1′-acetyl-2,3-dihydrospiro[benzofuran-2,4′-piperidine] 7 resulted in a 5-nitro derivative.     

An efficient diastereoselective synthesis of spiro pyrido[2,1-b][1,3]oxazines via a novel pyridine-based three-component reaction

The zwitterions generated from pyridine and dialkyl acetylenedicarboxylate (DAAD) reacted with benzofuran-2,3-diones to form highly substituted spiro pyrido[2,1-b][1,3]oxazines in good to high yields without using a catalyst.     

Synthesis of Functional Derivatives of Benzofuran-5,6-dicarboxylic Acids

Russian Journal of General Chemistry - Synthetic routes to novel substituted benzofuran-5,6-dicarboxylic acids and furo[2,3-f]isoindole-5,7-diones via acid hydrolysis of the corresponding...     

Facile synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones using monobromomalononitrile (MBM) as an efficient organo-brominating agent

An efficient methodology for the synthesis of 3H,3′H-spiro[benzofuran-2,1′-isoindole]-3,3′-diones has been developed where monobromomalononitrile (MBM) has been employed as a non-hazardous brominating agent under ambient reaction condition. The intrinsic advantages of the methodology are the utilization of simple and easily available starting materials and non-toxic reagents, operational simplicity, and good yields of the products with high atom-economy.     

Synthesis of spiro[2H-indole-2,1′-1H-isoindole]-3,3′-diones,spiro[1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones and spiro[benzofuran-2,1′-isobenzofuran]-3,3′-diones via transannular reactions of eight membered ring intermediates

An auto oxidation-rearrangement product 4 was isolated from a high dilution reaction of ninhydrin with 3,4,5-trimethoxyaniline in water. A general synthesis of this compound and its derivatives 4–6 was devised by oxidation of tetrahydroindeno[1,2-b]indol-10-ones 1–3 with sodium periodate to give isoindolo[2,1-a]-indole-6,11-diones 4–6 in good yield. Compounds 4–6 can be easily transformed into spiro[1H-isobenzofuran-1,2′-2H-indole]-3,3′-diones 8–10 , spiro[2H-indole-2,1′-1H-isoindole]-3,3′-diones 11–13 and isoindole[1,2-a:2′,1′-b]pyrimidine-5,15-diones 15, 16 in high yields. Analogous reactions were performed on 3-amino-5a, 10a-dihydroxybenzo[b]indeno[2,1-d]furan-10-one ( 17 ) to give a dibenzoxocintrione 18 , spiro-[benzofuran-2,1′-isobenzofuran]-3,3′-dione 19 and an isoindol-1-one 20 .     

Synthesis of 2,3,3a,8 a-tetrahydrofuro[2,3-b] benzofuran-2-one from coumarin

4-Vinyl-3,4-dihydrocoumarin, which is obtained in two steps from 3-(2-benzyloxyphenyl)allyl alcohol, was converted to 2,2,3a,8a-tetrahydrofuro[2,3-b]benzofuran-2-one by oxidation and rearrangement.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–750, June, 1976.     

苯并呋喃-2,3-二酮和丙酮的不对称Aldol反应

以脯氨酸作为催化剂催化苯并呋喃-2,3-二酮与丙酮的不对称Aldol反应, 高选择性地合成了一系列3位含有手性季碳中心的苯并呋喃酮类化合物.     

Silica sulfuric acid: an efficient reusable heterogeneous solid support for the synthesis of 3H,3′H-spiro[benzofuran-2,1′isobenzofuran]-3,3′-diones under solvent-free condition

A highly efficient protocol for the library synthesis of biologically important 3H,3′H-spiro[benzofuran-2,1′isobenzofuran]-3,3′-diones has been developed by employing silica sulfuric acid (SSA) as solid acid support under solvent-free condition. The dual characteristics of SSA, as an activating agent as well as oxidizing agent, have been well exposed in these syntheses. The intrinsic advantages of the methodology are the use of solvent-free reaction condition without using any toxic reagents or metal catalyst, operational simplicity, recyclability of the solid support, good availability of the starting materials, and excellent yields which make the method attractive, economic, and ‘benign by design’.     

Novel tetracyclic spiropiperidines. II. Synthesis of 2-aryl-2,3-dihydrospiro[benzofuran-3,4′-piperidines]

A series of 2-aryl-2,3-dihydropsiro[benzofuran-3,4′-piperidines] has been synthesized as potential psychotropic agents via an efficient intramolecular fluorine displacement reaction. Treatment of a key intermediate, 4-cyano-4-(2-fluorophenyl)-1-methylpiperidine ( 2 ), with a large excess of phenylmagnesium bromide in refluxing tetrahydrofuran led to some 2-arylspiro[3H-indole-3,4′-piperidine] derivatives, 10 and 11 , whose structures are elucidated on the basis of chemical and spectral evidence.     

Synthesis of formyl and carboxy derivatives of heterocycles by modification of 2-(2-aminovinyl)- benzofuran-5,6-dicarbonitriles

Procedures have been developed for the synthesis of 2-formylbenzofuran-5,6-dicarbonitriles, 5,6-dicyanobenzofuran-2-carboxylic acids, and formyldibenzo[b,d]furan-2,3-dicarbonitriles by modification of 2-(2-aminovinyl)benzofuran-5,6-dicarbonitriles with sodium periodate or Vilsmeier reagent.     

Asymmetric Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to nitroolefins catalyzed by a bifunctional tertiary-amine thiourea

The current work reports an organocatalytic strategy for the asymmetric catalysis of chiral benzofuran-2(3H)-ones bearing 3-position all-carbon quaternary stereocenters. Accordingly, highly enantioselective Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to nitroolefins have been developed by utilizing a bifunctional tertiary-amine thiourea catalyst. The reactions accommodate a number of nitroolefins and 3-substituted benzofuran-2(3H)-ones to give the desired chiral benzofuran-2(3H)-one products with moderate to excellent yields (up to 98%) and moderate to very good selectivities (up to 19?:?1 dr and up to 91% ee). Theoretical calculations using the DFT method on the origin of the stereoselectivity were conducted. The effect of the nitroolefin substituent position on the stereoselectivity of the Michael addition reaction was also theoretically rationalized.     

Chiral biscinchona alkaloid promoted asymmetric allylic alkylation of 3-substituted benzofuran-2(3H)-ones with Morita-Baylis-Hillman carbonates

A highly diastereo- and enantioselective asymmetric allylic alkylation reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and MBH carbonate by a chiral biscinchona alkaloid catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 97%) with very good diastereo- (up to 98:2 dr) and enantioselectivities (up to 95% ee).     

Chiral amine thiourea-promoted enantioselective Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to maleimides

A highly diastereo- and enantioselective Michael addition reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and maleimides by a chiral bifunctional thiourea-tertiary amine catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 99%) with very good diastereo- (up to >20:1 dr) and enantioselectivities (up to 97% ee).     

One-pot reaction for the concise synthesis of spiro[benzofuran-2,2′-naphthalen]-1′-one derivatives

A novel one-pot two-step protocol has been developed to synthesize various spiro[benzofuran-2,2′-naphthalen]-1′-one derivatives from the three-component reaction of tetralones, 2-hydroxyphenyl functionalized α,β-unsaturated ketones, and iodine. One C–C bond and one C–O bond have formed during this process. The notable features of this protocol are simple and mild reaction conditions, applicable to a wide range of readily available starting materials, good yields (up to 91%), and excellent stereoselectivities (up to 97:3).     

Heterocyclic analogs of 5,12-naphthacenequinone 9*. Study of the synthesis and reactivity of 4,11-dimethoxynaphtho[2,3-<Emphasis Type="Italic">f</Emphasis>]isatin-5,10-diones

A preparative method has been developed for N-alkyl 4,11-dimethoxynaphtho[2,3-f]isatin-5,10-diones. Condensation reactions with several N- and C-nucleophiles have been carried out to give the corresponding derivatives at position 3. An efficient method has been discovered for the demethylation of the N-alkyl-4,11-dimethoxynaphtho[2,3-f]isatin-5,10-diones to give a high yield of N-substituted 4,11-dihydroxynaphtho[2,3-f]isatin-5,10-diones. Successive halogenation using phosphorus penta-chloride and acylation of tert-butylamine by the intermediate 2-chloro derivative converted 4,11-di-methoxynaphtho[2,3-f]isatin-5,10-dione to the 2-amino-3H-naphtho[2,3-f]indole-3,5,10-trione derivative.     

A facile synthesis of novel benzofuran-2-yl(9-methyl-9H-carbazol-3-yl)methanones

A facile synthesis of hitherto unreported benzofuran-2-yl(9-methyl-9H-carbazol-3-yl)methanones (3a?Cl) is described. The synthesis mainly relies on the ultrasound-assisted Rap?CStoermer reaction of 3-chloroacetyl-9-methyl-9H-carbazole (1) with a variety of salicylaldehydes, as well as 2-hydroxy-1-naphthaldehyde (2) in CH₃CN, with the presence of PEG-400 as a catalyst. This procedure offers easy access to benzofuran-2-yl(carbazolyl)methanone derivatives in a short reaction time and the products are achieved in good yields.     

Oxalylation of the 3-oxo-<Emphasis Type="Italic">N</Emphasis>-phenyl-3-R-propanethioamides

Oxalylation of 3-oxo-N-phenyl-3-R-propanethioamides in aprotic solvents in the temperature range from −40°C to +20°C results in 4-acyl-5-phenylamino-2,3-dihydrothiophene-2,3-diones and 2-(2-oxo-2-R-ethylidene)-3-phenyl-1,3-thiazolidine-4,5-diones, while in the presence of potassium carbonate, potassium 4-acyl-2,3-dioxo-1-phenyl-2,3-dihydro-1H-pyrrole-5-thiolates are formed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 757-760, March, 2005.     

Synthesis and characterization of new thermally stable copoly(ester–amide)s from diester–dicarboxylic acids

Three new aromatic diester–dicarboxylic acids containing furan rings, namely, benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-phenyl ester-4,4^′-dicarboxylic acid, benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-phenyl ester-3,3^′-dicarboxylic acid and benzofuro[2,3-b]benzofuran-2,9-dicarboxyl-bis-naphthyl ester-2,2^′-dicarboxylic acid were synthesized by the reaction of benzofuro[2,3-b]benzofuran-2,9-dicarbonyl chloride with 4-hydroxybenzoic acid, 3-hydroxybenzoic acid and 3-hydroxy-naphthalene-2-carboxylic acid, respectively. Diester–dicarboxylic acids were characterized by FT-IR and NMR spectroscopy and elemental analyses. Then, these monomers were converted to aromatic copoly(ester–amide)s by their reaction with various aromatic diamines via the direct polycondensation. These polymers were characterized by viscosity measurements, solubility tests, FT-IR, Ultraviolet and ¹H-NMR spectroscopy and thermogravimetry. The polymers with inherent viscosities in the range of 0.16–0.37 dl/g in dimethyl sulfoxide at 30 °C were obtained in high yield. Most of them dissolved readily at room temperature in polar solvents. The synthesized copoly(ester–amide)s possessed glass-transition temperatures from 210–255 °C. The copoly(ester–amide)s exhibited excellent thermal stabilities and had 10% weight loss at temperature above 295 °C under nitrogen atmosphere.     

5-(4-叔丁氧基羰基哌嗪基)苯并呋喃-2-甲酸乙酯的合成

5-溴苯并呋喃-2-甲酸乙酯与4-叔丁氧基羰基哌嗪进行Buchwald-Hartwig偶联反应,若催化剂是Pd(OAc)2/BINAP,碱是Cs2CO3,则产物主要是5-(4-叔丁氧基羰基哌嗪基)苯并呋喃-2-甲酸乙酯,转化率达70%;若催化剂是Pd(dba)2/P(t-Bu)3,碱是叔丁醇钾,则产物中几乎没有5-(4-叔丁氧基羰基哌嗪基)苯并呋喃-2-甲酸乙酯.文中讨论了影响这个Buchwald-Hartwig偶联反应的因素.     

Kinetic resolution of 1-(benzofuran-2-yl)ethanols by lipase-catalyzed enantiomer selective reactions

Kinetic resolution of racemic 1-(benzofuran-2-yl)ethanols rac-1a–d was performed by lipase-catalyzed enantiomer selective acylation (E≫100) yielding (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d and (1S)-1-(benzofuran-2-yl)ethanols (S)-1a–d in highly enantiopure form. The degree of enantiomer selectivity for enzymatic alcoholysis/hydrolysis processes starting from racemic 1-acetoxy-1-(benzofuran-2-yl)ethane rac-2 was also tested under various conditions including supercritical CO₂ medium. Racemization-free lipase-catalyzed ethanolysis of the (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d yielded almost quantitatively the enantiopure (1R)-1-(benzofuran-2-yl)ethanols (R)-1a–d.