Efficient and Convenient Synthesis of 1,4-Benzoxazines, 1,4-Benzothiazines,Spiro-1,4-benzoxazines,and Spiro-1,4-benzothiazines

An efficient, convenient synthesis of 1,4-benzoxazines, 1,4-benzothiazines, spiro-1,4-benzoxazines, and spiro-1,4-benzothiazines derivatives was accomplished in good yields via the novel intramolecular cyclization mediated by mild base K₂CO₃ in ethanol solvent. A variety of substrates can participate in the process with good yields, making this methodology have broad applicability. All the structures of synthesized compound have been confirmed by spectral analysis.

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Synthesis and rearrangement of 4-imino-4H-3,1-benzoxazines

Summary N-Acylanthranilamides react with dibromotriphenylphosphorane in the presence of triethylamine as HBr captor to give 4-imino-4H-3,1-benzoxazines in good yields. If the reaction is carried out without acid acceptor, N-acetylanthranilamides yield 2-methyl-4-quinazolones, whereas N-benzoylanthranilamides give 2-phenyl-4-imino-4H-3,1-benzoxazines. It has also been found that 2-methyl-4-imino-4H-3,1-benzoxazines rearrange under the influence of HCl or HBr into the respective 2-methyl-4-quinazolones; 2-phenyl-4-imino-4H-3,1-benzoxazines, however, do not undergo such a rearrangement.

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Synthese und Umlagerung von 4-Imino-4H-3,1-benzoxazinen

Zusammenfassung Die Umsetzung von N-Acyl-anthranilsäure-amiden mit Triphenyldibromphosphoran in Gegenwart von Triethylamin als HBr-Akzeptor führt mit guten Ausbeuten zu 4-Imino-4H-3,1-benzoxazinen. Wird die Reaktion ohne säurebindendes Mittel durchgeführt, dann entstehen aus N-Acetyl-anthranilsäure-amiden 2-Methylchinazolone-4, jedoch erhält man aus N-Benzoylanthranilsäure-amiden 2-Phenyl-4-imino-4H-3,1-benzoxazine. 2-Methyl-4-imino-4H-3,1-benzoxazine erleiden unter dem Einfluß von HBr oder HCl eine Umlagerung in entsprechende 2-Methylchinazolone-4, während 2-Phenyl-4-imino-4H-3,1-benzoxazine zu einer solchen Umlagerung nicht befähigt sind.

     

Reeve's synthesis of 2-imino-4-thiazolidinone from alkyl (aryl) trichloromethylcarbinol revisited, a three-component process from aldehyde, chloroform and thiourea

An efficient synthesis of 2-imino-4-thiazolidinones from readily accessible alkyl (aryl) trichloromethylcarbinols and thioureas under mild conditions is reported. A one-pot three-component synthesis of the title compounds from aldehyde, chloroform and thiourea is also developed for the first time     

Microwave-assisted one-pot regioselective synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines

A protocol for regioselective one-pot synthesis of 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines under controlled microwave heating has been developed. Starting from commercially available 2-aminophenols, a base-mediated regioselective O-alkylation took place with 2-bromoalkanoates to give the acyclic intermediates, which underwent spontaneously an intramolecular amidation reaction to furnish 2-alkyl-3,4-dihydro-3-oxo-2H-1,4-benzoxazines in 44-82% yields. For the acyclic intermediate possessing an electron-withdrawing group, microwave heating was necessary for the annulation reaction.     

Efficient synthesis of 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes via copper-catalyzed domino reaction

A domino approach to 2-imino-1,2-dihydroquinolines and 2-imino-thiochromenes from sulfonyl azides, alkynes, and 2-acyl anilines or the potassium salt of 2-mercapto-benzaldehyde has been developed. This one-pot method is efficient and versatile.     

The Huisgen 1,4-dipolar cycloaddition involving isoquinoline, dimethyl butynedioate and activated styrenes: a facile synthesis of tetrahydrobenzoquinolizine derivatives

A three-component reaction involving isoquinoline, dimethyl butynedioate and electrophilic styrenes is described. The reaction proceeds through a Huisgen 1,4-dipolar cycloaddition pathway.     

Cobalt(II) complexes bearing 2-imino-1,10-phenanthroline ligands: synthesis, characterization and ethylene oligomerization

A series of cobalt(II) complexes containing 2-imino-1,10-phenanthrolines have been synthesized and characterized by elemental and spectroscopic analysis. The molecular structures of complexes 2, 3, 8 and 14 were confirmed by X-ray diffraction analysis. On treatment with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), these cobalt(II) complexes show moderate to high catalytic activities for ethylene oligomerization and butene predominates among the oligomers produced. The parameters of the reaction conditions and the effects of the ligands environment were investigated. To cite this article: S. Jie et al. C. R. Chimie 9 (2006).     

One-pot synthesis of novel pyrrolo-1,4-benzoxazines via a three- component reaction of 2-amino phenols,acetylenic esters and nitrostyrene derivatives简

A simple and efficient synthetic protocol has been developed using a one-pot, three-component reaction involving 2-amino phenols, dialkyl acetylene dicarboxylates and nitrostyrene derivatives. Utilizing this protocol, a variety of novel pyrrolo-1,4-benzoxazine derivatives were synthesized in excellent yields.     

Three-component cascade reaction synthesis of polycyclic 1,4-dihydropyridine derivatives in water

An efficient and straightforward synthesis of polycyclic 1,4-dihydropyridine derivatives has been developed by reacting heterocyclic ketene aminals (HKAs) with 1,3-cyclohexanedione derivatives and a number of substituted salicylaldehyde, respectively, via three-component cascade reactions in water. This strategy provides an efficient and environmentally friendly approach for easy access to various new fused polycyclic 1,4-dihydropyridine derivatives without the need of organic solvents in moderate to good yields.     

Three-component reaction of imidazoles,cyanophenylacetylene, and chalcogens: stereoselective synthesis of 3-alkenyl-2-imidazolethiones and -selones

The three-component reaction of 1-substituted imidazoles, cyanophenylacetylene, and elemental sulfur or selenium proceeds readily (for sulfur at room temperature without solvent, and for selenium in boiling MeCN) to stereoselectively afford 3-(Z)-cyanophenylethenyl-2-imidazolethiones or -selones in yields ranging 39–97% (for thiones) and 39–84% (for selones). In this reaction, tellurium is inactive both under the above conditions and upon heating (50–55 °C) in DMSO, instead, only the C(2)-vinylation of the imidazole ring in up to 98% yield takes place. The Z-stereoselectivity of the reaction is close to 100% (for sulfur) and reaches 91–99% (for selenium). The reaction involves the zwitterionic adduct of imidazoles with cyanophenylacetylene, which converts to the carbene via proton transfer (from the imidazole 2 position to the carbanionic site of the zwitterion) further reacting with chalcogens.     

A new efficient method for the synthesis of 3,4-dihydro-2H-1,4-benzoxazines via iodocyclization

An efficient approach for the synthesis of 3,4-dihydro-2H-1,4-benzoxazine derivatives is described by molecular iodine- mediated cyclization. The reaction condition is very simple, offers easy isolation, and affords good to excellent yields of the products.     

A general synthesis of N-substituted 1,4-benzoxazine- and 1,4-benzothiazine-2-carboxylates via copper-catalyzed intramolecular amination of arylbromides

Starting from ortho-bromosubstituted phenoxyacetates or (phenythio)acetates and primary amines, various N-substituted 4H-1,4-benzoxazine- and 4H-1,4-benzothiazine-2-carboxylates were synthesized in moderate to high yields by using a Cu(I)-catalyzed Ullmann-type cyclization as a key step. The method is simple to operate, tolerates many functional groups and does not require any additives.     

Synthesis of cyclopropyl-substituted 4H-3,1-benzoxazines from 2-amino-phenyl cyclopropyl ketones and 2-cyclopropanoylaminoacylbenzenes

2- and 4-cyclopropyl- and 2,4-dicyclopropyl-substituted 4H-3,1-benzoxazines were synthesized by the intramolecular acid catalyzed heterocyclization of ortho-acylamino-substituted benzyl alcohols, obtained from 2-aminophenyl cyclopropyl ketones and 2-cyclopropanoylaminoacylbenzenes. Translated from Khimiya Geterotsicklicheskikh Soedinenii No. 2, 252-268, February, 2009.     

Synthesis of some new N,N''-diaryisubstituted methylene-bis-dihydro-2H-1,3-benzoxazines

The synthesis of a new series of six-membered N,N'-diarylsubstituted methylene-bis-dihydro-2H-1,3-benzoxazines (Sa-e) was achieved in excellent yields by Mannich-type condensation of N,N'-diarylsubstituted methylene-bis-o-hydroxybenzyl amines (4a-e) with formaldehyde in chloroform at reflux. These amines (4a-e) were obtained by the reduction of N,N'-diarylsubstituted methylene-bis-o-hydroxybenzyl imines (3a-e) with NaBH4, which inturn were obtained by the condensation of methylene-bis-salicylaldehyde (2) with various substituted arylamines.     

Synthese und Reaktivität von 2- und 3-hydroxylierten Dihydro-1,4-Benzoxazinen

2 can be pyrrolized to yield3 a, which in turn may be hydrolyzed with HCl to3 b. Acetylation of3 a followed by a reaction with trifluoroacetic acid (TFA) gives3 e. Elimination of ethanol from3 a or of water from3 e is not possible. Treatment of1 a with pyridine/acetic anhydride andTFA or with acetic acid/acetic anhydride affords4 a and4 b, resp. Reaction of4 b in benzene/p-toluenesulfonic acid for 2 hours yields both ethers5I and5II, whereas after 6 hours 4-acetyl-4H-1,4-benzoxazine (6) is obtained. The structures of all products are established by chemical and spectroscopic methods.

Teile aus der DissertationW. Kropp, Universität Wien, 1977.     

A new and efficient one-pot synthesis of 2-hydroxy-1,4-dihydrobenzoxazines via a three-component Petasis reaction

The secondary amines synthesized by the reaction between 2-aminophenols and aromatic aldehydes, via the reduction of the corresponding imines, were employed in the synthesis of new 2-hydroxy-2H-1,4-benzoxazine derivatives through a one-pot Petasis multicomponent reaction in good to excellent yields.     

Synthesis, characterization and ethylene oligomerization studies of nickel complexes bearing 2-imino-1,10-phenanthrolines

A series of nickel (II) complexes ligated by 2-imino-1,10-phenanthrolines were synthesized and characterized by elemental and spectroscopic analysis as well as by single-crystal X-ray crystallography. X-ray crystallographic analysis reveals complexes 3, 5, 7 and 11 as the five-coordinated distorted trigonal-bipyramidal geometry. Upon activation with Et₂AlCl, these complexes exhibited considerably high activity for ethylene oligomerization (up to 3.76 × 10⁷ g mol⁻¹(Ni) h⁻¹ for 12 with 10 equiv. of PPh₃). The ligand environment and reaction conditions significantly affect the catalytic activity of their nickel complexes.     

Three-component reaction for the C2-functionalization of 1-substituted imidazoles with acetylenic ketones and isocyanates

An efficient method for the direct C2-amidation of 1-substituted imidazoles with acetylenic ketones and isocyanates is reported. This three-component procedure has the advantages of catalyst-free, operational simplicity, mild reaction conditions, and good to excellent yields.     

A Simple Indirect Route for the Synthesis of N-Alkyl-4-imino-1,4-dihydro-2H-3,1-benzoxazin-2-ones

Summary. Novel N-alkyl-4-imino-1,4-dihydro-2H-3,1-benzoxazin-2-ones were synthesized in a single step by Baeyer–Villiger oxidation of N-alkyl-3-imino-2-indolinone derivatives in high yields. The structures of the products were determined by spectral data and by X-ray diffraction. Besides their novel structures, these compounds may have important biological activities and industrial applications.