Zur Umsetzung von 8a-Methoxy-3,4-dihydro-2H-1,4-benzoxazin-6(8aH)-onen mit Diazoalkanen, 2. Mitt.

Summary 8a-Methoxy-3,4-dihydro-2H-1,4-benzoxazin-6(8aH)-ones2 undergo regio- and stereospecific 1,3-dipolar cycloaddition reactions with diazomethane or diazoethane to yield 3,4,6a,9,9a,9b-hexahydro-pyrazolo[3,4-h][1,4]benzoxazin-6(2H)-ones3, which slowly isomerize in solution to give the 3,4,8,9,9a,9b-hexahydro-pyrazolo[3,4-h][1,4]benzoxazin-6(2H)-ones5. The carbon of the diazoalkane dipole is attached to carbon C-8 of the benzoxazinone. The structures of the obtained products were determined by¹H- and¹³C-NMR spectroscopy. An X-ray crystal structure analysis of3 a was carried out at room temperature:C₁₁H₁₅N₃O₃,M _r =237.26, orthorhombic, Pc2₁n,a=9.173 (5),b=9.133 (4),c=13.281 (6),V=1112.6 (9) ų,Z=4,d _x =1.416 g/cm^–3, =0.93 cm^–1,R=4.33%,R _w =3.95% (919 observations, 168 parameters).

Herrn Prof. Dr. W. Fleischhacker zum 60. Geburtstag gewidmet     

Zur Umsetzung von 3,4-Dihydro-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-onen mit Diazoalkanen, 1. Mitt.

Summary 3,4-Dihydro-8a-methoxy-2H-1,4-benzoxazin-6(8aH)-ones — quinol derivatives of 2-hydroxyethylamino-1,4-benzoquinones — react with diazoalkanes to yield 2,3,9a,9b-Tetrahydro-9H-pyrazolo[3,4-h]-1,4-benzoxazin-6(6aH)-ones (3). Their structures were established on basis of NMR-techniques including two-dimensional experiments. The orientation phenomena of the reaction is discussed.

     

Indium-mediated regioselective mono-allylation of 1,5-dicarbonyl compounds and dehydrative cyclization to 2,3-dihydro-4H-pyran-4-ones and 3,4-dihydro-2H-[1,4]oxazines

An indium-mediated Barbier type mono-allylation of 1,5-dicarbonyl compounds and a subsequent acid-catalyzed dehydrative cyclization afforded 2,3-dihydro-4H-pyran-4-ones and 3,4-dihydro-2H-[1,4]oxazines.     

Reactions of 3-hydroxy-1,2-dihydroquinazolin-4-ones with aldehydes

The reactions of 3-hydroxy-2-(2-hydroxyalkyl)- [or (2-hydroxyaryl)]-1,2-dihydro-quinazolin-4-ones with formaldehyde or acetaldehyde afford 1,3-oxazino[3,4-a]quinazolin-4-one derivatives. The reactions with other aldehydes RCHO and 3-hydroxy-2-R′-1,2-dihydroquinazolin-4-ones can give 3-hydroxy-2-R-1,2-dihydroquinazolin-4-ones, 2-substituted quinazolin-4-ones, or dianthranilide. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2523–2526, December, 1998.     

Crystal Structures of 5-Nitro- and 5-Ethoxycarbonyl-Substituted 6-Phenyl-4-(3-fluorophenyl)-3,4-dihydro-(1H)-pyrimidin-2-ones

The crystal structures of 5-nitro- and 5-ethoxycarbonyl-substituted 6-phenyl-4-(3-fluorophenyl)-3,4-dihydro-(1H)-pyrimidin-2-ones were determined by X-ray diffraction analysis. Conformational peculiarities of the structures have been revealed and compared with data for other biologically active dihydropyrimidinones.     

1,1-Dichloro-2,2,2-trihaloethyl Isocyanates and N-(1-Chloro-2,2,2-trihaloethylidene)urethanes in the Synthesis of 4-Trihalomethyl-2H-1,3-benzoxazin-2-ones

4-Trihalomethyl-2H-1,3-benzoxazin-2-ones have been synthesized by the reaction of 1,1-dichloro-2,2,2-trihaloethyl isocyanates or N-(1-chloro-2,2,2-trihaloethylidene)urethanes with 3-dialkylamino(alkoxy)phenols. The character of the products from the addition of nucleophiles has been shown to depend on the nature of the nucleophile and the trihalomethyl group.     

Optically active 4-amino-4-aryl-5,5,5-trifluoropentan-2-ones: Versatile reagents for synthesis of chiral 4-trifluoromethyl-3,4-dihydroazin-2-ones

A cyclocondensation of disubstituted (thio)ureas and isocyanates derived from enantiomerically enriched 4-amino-4-aryl-5,5,5-trifluoropentan-2-ones affords a novel synthetic access to chiral 4-trifluoromethyl-substituted 3,4-dihydropyrimidin-2(1H)-(thi)ones and 3,4-dihydro-1,3-oxazin-2-ones, respectively.     

Base-promoted 1,3-dipolar cycloaddition reaction of nitrile oxides with methyl 1,4-dioxo-1,4-dihydronaphthalene-2-carboxylate for the construction of naphtho[2,3-d]isoxazole-4,9(3aH,9aH)-diones

A base mediated 1,3-dipolar cycloaddition reaction of methyl 1,4-dioxo-1,4-dihydronaphthalene-2-carboxylate with nitrile oxides in situ generated from N-hydroximoyl chlorides was achieved. With this developed protocol, a range of structurally diverse naphtho[2,3-d]isoxazole-4,9(3aH,9aH)-dione derivatives were smoothly obtained in high yields (up to 95%) with up to >20:1 regioselectivities and >20:1 diastereoselectivities under mild conditions. The promising applicability of the protocol was also demonstrated by the further transformations.     

Control of electron demand in the cycloadditions of 2(H)-1,4-oxazin-2-ones

3-Methoxy-5-chloro-6-methyl-2(H)-1,4-oxazin-2-one 4, 3-methoxy-5-chloro-6-phenyl-2(H)-1,4-oxazin-2-one 5, 3-phenylsulfenyl-5-chloro-6-methyl-2(H)-1,4-oxazin-2-one 6, and 3-phenylsulfenyl-5-chloro-6-phenyl-2(H)-1,4-oxazin-2-one 7, are ambident dienes and undergo Diels-Alder cycloadditions with electron neutral, rich and deficient dienophiles.     

Synthesis of 4-Amino-6-R-4,5-dihydro-3-phenacylthio-1,2,4-triazin-5-ones and 8H-3-R-7-Aryl-1,2,4-triazino[3,4-b][1,3,4]thiadiazin-4-ones

A study was carried out on the reaction of 4-amino-6-R-2,3,4,5-tetrahydro-3-thioxo-1,2,4-triazin-5-ones with halo ketones in alkaline media to yield 4-amino-6-R-4,5-dihydro-3-phenacylthio-1,2,4-triazin-5-ones, which then convert to 8H-3-R-7-aryl-1,2,4-triazino[3,4-b][1,3,4]thiadiazin-4-ones.     

Synthesis of 3,4-dihydrobenzo[g]isoquinoline-1(2H)-ones and 3,4-dihydroisoquinoline-1(2H)-ones skeleton via intramolecular electrophilic cyclization

An original alternative approach to isoquinolines based on the installation of a benzene nucleus on a performed heterocyclic ring. Synthesis of 3,4-dihydrobenzo[g]isoquinoline-1(2H)-ones and 3,4-dihydroisoquinoline-1(2H)-ones via intramolecular electrophilic cyclization of 3,4-disubstituted lactams is reported.     

Interaction of 3-p-toluoyl-1,2-dihydro-4H-pyrrolo-[2,1-c][1,4]benzoxazine-1,2,4-trione with benzylamine. Synthesis and crystal and molecular structure ofZ-3-(1-benzyl-2-hydroxy-4,5-dioxo-2-p-tolyltetrahydropyrrol-3-idene)-3,4-dihydro-2H-1,4-benzoxazin-2-one

3-p-Toluoyl-1,2-dihydro-4H-pyrrolo-[2,1-c][1,4]benzoxazine-1,2,4-trione reacts with benzylamine to yieldZ-3-(1-benzyl-2-hydroxy-4,5-dioxo-2-p-tolyltetrahydropyrrol-3-idene)-3,4-dihydro-2H-1,4-benzoxazin-2-one. The crystal and molecular structure of the latter compound was studied by X-ray structural analysis. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 566–569, March, 1997.     

Chemoenzymatic preparation of optically active 4-aryl-5-carboxy-6-methyl-3,4-dihydro-2(1H)-pyridone derivatives

A series of racemic 4-aryl-5-(tert-butoxycarbonyl)-6-methyl-3,4-dihydro-2(1H)-pyridones have been prepared by means of a modified Hantzsch reaction using commercially available starting materials. An easy removal of the tert-butyl group of these pyridones and subsequent reaction with cesium carbonate and chloromethyl 2-methylpropanoate provided us suitable substrates (±)-5 to be used in lipase-catalyzed hydrolysis reactions. Lipase B from Candida antarctica (CAL-B) was the most adequate lipase in the hydrolysis of (±)-5. Despite the low enantioselectivity values obtained (E≤12), several optically active pyridone derivatives were finally isolated with high enantiomeric excesses (ee≥91%) and moderate yields.     

Reactions of cyclic 1,3-dicarbonyl compounds with 1,2(1,4)-dihydro-1-methyl-2(4)-methylene-N-heterocycles. A new access to 6,12-methano-dibenz[d,g]-[1,3]oxazocinones

Summary The enamine-type methylene-N-heterocycles1–5 react with cyclic 2-ethoxymethylene-1,3-dicarbonyl compounds6 to give 2-[2-(hetarylidene)ethylidene]-1,3-dicarbonyl compounds7–14. The result of the reactions between 1,2-dihydro-1-methyl-2-methylene-quinoline (1a) and cyclic 1,3-dicarbonyl compounds depends on the nature of the dihydro intermediatesA/B. Dehydrogenation of keton intermediatesA results in 2-(1,2-dimethyl-4(1H)-quinolylidene)-1,3-dicarbonyl compounds17–21. Enol intermediatesB with 6-membered dicarbonyl ring form 6,12-methano-dibenz-[d,g][1,3]oxazocinones22–25.¹H NMR spectra and X-ray structure analysis prove the structure of23.

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Reaktionen cyclischer 1,3-Dicarbonylverbindungen mit 1,2(1,4)-Dihydro-1-methyl-2(4)-methylen-N-heterocyclen. Ein neuer Zugang zu 6,12-Methano- dibenz[d,g][1,3]oxazocinonen

Zusammenfassung Aufgrund ihres Enamincharakters reagieren die Methylen-N-heterocyclen1–5 mit cyclischen 2-Ethoxymethylen-1,3-dicarbonylverbindungen6 zu den 2-[2-(Hetaryliden)ethyliden]-1,3-dicarbonylverbindungen7–14. Das Ergebnis der Reaktionen zwischen 1,2-Dihydro-1-methyl-2-methylen-chinolin (1a) und cyclischen 1,3-Dicarbonylverbindungen hängt von der Natur der zwischenzeitlich entstehenden DihydroverbindungenA/B ab. Die Intermediat-KetoneA gehen durch Dehydrierung während der Reaktion in die 2-(1,2-Dimethyl-4(1H)chinolyliden)-1,3-dicarbonylverbindungen17–21 über. Die Intermediat-EnoleB mit sechsgliedrigem Dicarbonylring bilden in intramolekularer Reaktion die 6,12-Methano-dibenz[d,g][1,3]oxazocinone22–25, deren Struktur am Beispiel der Verbindung23 durch¹H-NMR sowie durch Röntgenkristallstrukturanalyse bewiesen wird.

     

Synthesis of 3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines using ammonium carbonate in water

Various known and new 3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines are prepared efficiently via Biginelli and Hantzsch reactions using ammonium carbonate in water. Competition between Biginelli and Hantzsch reactions is observed with pyridine carbaldehydes. Using this methodology, Hantzsch esters are synthesized in higher yields and purities than with other procedures without the use of a catalyst or an organic solvent.     

Regioselective dehydrogenation of 3,4-dihydropyrimidin-2(1H)-ones mediated by ceric ammonium nitrate

Ceric ammonium nitrate (CAN) has been explored for the regioselective oxidation of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs). Interestingly, we obtained ethyl 2,4-dioxo-6-phenyl-tetrahydropyrimidin-5-carboxylates as the major products during the oxidation of DHPMs by CAN/AcOH at 80 °C. The reaction afforded a mixture of products while employing CAN in organic solvents without additives. However, the regioselective dehydrogenated product, ethyl 6-methyl-4-aryl(alkyl)-pyrimidin-2(1H)-one-5-carboxylate was obtained by performing the reaction with NaHCO₃. The single crystal X-ray crystallography of ethyl 6-methyl-4-(2-phenyl)-pyrimidin-2(1H)-one-5-carboxylate revealed that the oxidized product existed in amidic form rather than aromatized enol form of pyrimidines. The efficiency of the present protocol enabled the synthesis of structurally diverse pyrimidines in moderate to good yields under milder reaction conditions.     

Separation of enantiomers and diastereomers of 4-hydroxy-2H-1,4-benzoxazin-3(4H)-one derivatives by capillary electrophoresis

Summary A high performance capillary electrophoresis (HPCE) procedure for the enantioseparation of the methyl acetals3 and4 of the natural products DIBOA1 and DIMBOA2, respectively, has been developed using borate buffers (pH 9–10 range), cyclodextrins as chiral additives and addition of up to 20% methanol. A mixture of GDIBOA5 and GDIMBOA6 of natural origin was also clearly separated. HPCE proved to be superior to HPLC by the first separation of GDIBOA5 and three of its diastereomers resulting from a synthetic approach to this acetalglucoside.     

Access to 4-substituted 3,4-dihydroquinolin-2(1H)-ones by an unusual radical cyclisation of a secondary amide

A novel route to 3,4-dihydroquinolin-2(1H)-ones involving two radical addition steps is reported, starting from readily accessible xanthates and N-aryl-3-butenamides.