4-β-D-Ribofuranosyl-1,2,4-triazin-3,5(2H,4H)-dione and 4-β-D-ribofuranosyl-6-methyl-1,2,4-triazin-3,5(2H, 4H)-dione

1982 ◽  
Vol 47 (3) ◽  
pp. 994-999 ◽  
Author(s):  
Hubert Hřebabecký
Keyword(s):  
Uv Irradiation ◽  
Sodium Methoxide ◽  
Methanolic Solution ◽  
Acid Catalyzed ◽  
Methyl Pyruvate

4-β-D-Ribofuranosyl-1,2,4-triazin-3,5(2H,4H)-dione (IX) and 4-β-D-ribofuranosyl-6-methyl-1,2,4,-triazin-3,5(2H,4H)-dione (XI) were prepared by cyclization of (Z)-4-β-D-ribofuranosyl-semicarbazones of methyl glyoxylate (VI) and methyl pyruvate (VIII) in the methanolic solution of sodium methoxide. A mixture of (E)- and (Z)-ribosylsemicarbazones III and IV was prepared by condensation of the ribosylsemicarbazide I with methyl dimethoxyacetate and a mixture of (E)-and (Z)-isomers V and VIII was obtained on condensation of I with methyl pyruvate. The (Z) isomer VI was prepared on acid-catalyzed isomerisation of the (E)-isomer III while the (Z)-isomer VIII was obtained on the UV-irradiation of isomer V.

Synthesis of Azocane- and Oxocane-Annulated Furans by a [2+2] Photocycloaddition–Ring-Opening Cascade

Synthesis ◽  
2020 ◽  
Author(s):  
Thorsten Bach ◽  
Xinyao Li ◽  
Christian Jandl
Keyword(s):  
Double Bond ◽  
Uv Irradiation ◽  
Alkyl Group ◽  
Ring Opening ◽  
Cascade Reaction ◽  
Coumarin Derivatives ◽  
Ring Opening Reaction ◽  
Acid Catalyzed ◽  
Subsequent Acid

AbstractThe title compounds were synthesized from readily available quinolone and coumarin derivatives by a cascade reaction (12 examples, 90–98% yield). The cascade comprised a [2+2] photocycloaddition which occurred upon sensitized irradiation at λ = 420 nm (or direct UV irradiation at λ = 366 nm) and a subsequent acid-catalyzed ring-opening reaction. A variety of substituents are compatible with the conditions and a 3-alkyl group in the coumarin (or quinolone) is crucial to achieve a high chemoselectivity. Key to the success of the ring opening is the formation of a 4,5,5a-trihydrocyclobuta-2H-furan containing a strained bridgehead double bond which stems from the allenyl group tethered to the 4-position of the starting materials.

Electrooxidative Conversion of Dibenzoylbenzene Dihydrazones into the Corresponding Bis-diazo Compounds and Bis-dimethyl Acetals

2005 ◽  
Vol 58 (7) ◽  
pp. 560 ◽  
Author(s):  
Mitsuhiro Okimoto ◽  
Kaori Numata ◽  
Kenta Tomozawa ◽  
Takamasa Shigemoto ◽  
Masayuki Hoshi ◽  
...  
Keyword(s):  
Sodium Methoxide ◽  
Diazo Compound ◽  
Catalytic Amount ◽  
Diazo Compounds ◽  
Purple Colour ◽  
Methanolic Solution

Several dibenzoylbenzene dihydrazones were electrochemically oxidized into the corresponding bis-dimethyl acetals in a methanolic solution containing sodium methoxide and a catalytic amount of KI. During electrolysis, the anolyte exhibited a characteristic deep purple colour, which strongly suggests the formation of a diazo compound as an intermediate. Such intermediates have been isolated in the electrooxidation of two dihydrazones.

scholarly journals Acid-catalyzed and photolytic reactivity of some unsaturated B-nor-5, 10-secosteroidal ketones

2003 ◽  
Vol 68 (4-5) ◽  
pp. 303-312 ◽  
Author(s):  
Mira Bjelakovic ◽  
Vladimir Pavlovic ◽  
Milan Dabovic ◽  
Ljubinka Lorenc
Keyword(s):  
Uv Irradiation ◽  
Intramolecular Cyclization ◽  
Unsaturated Compound ◽  
Acid Catalyzed

The acid-catalyzed reaction of (Z)- and (E)-B-nor-5,10-seco-ketones 2 and 3 resulted in an intramolecular cyclization to give the 5-hydroxy-A-nor-1?,5?-10(19)-methylidene derivative 8, the 5?-hydroxy-A-nor-1(10)-unsaturated compound 9 and the 5?,10?-dihydroxy A-nor-product 10, from the (Z)-isomer and the 5-hydroxy-A-nor-1?,5?-10(19)-methylidene product 11, from the (E)-isomer. Upon UV-irradiation, the (Z)- and (E)-seco-ketones 2 and 3 underwent a reversible (Z)/(E) and (E)/(Z)-isomerization and in addition to a transannular photocyclization to afford the 10(19)-methylidene derivatives 8 and 11, respectively, while photolysis of the 10(19)-methylidene-B-nor-5,10-seco-ketone 4 gave the oxetane derivative 12.

Total Synthesis of DL-Glucose, 3-O-Methyl-DL-glucose, and 3-Deoxy-DL-ribo-hexopyranose from 1,6:3,4-Dianhydro-β-DL-allo-hexopyranose, a Product Obtained from Acrolein Dimer

1971 ◽  
Vol 49 (20) ◽  
pp. 3342-3347 ◽  
Author(s):  
U. P. Singh ◽  
R. K. Brown
Keyword(s):  
Total Synthesis ◽  
Acid Hydrolysis ◽  
Sodium Methoxide ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Barium Hydroxide ◽  
Lithium Aluminum ◽  
Methyl Glycoside ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The reaction of butyllithium in ether with 1,6:2,3-dianhydro-4-deoxy-β-DL-ribo-hexopyranose (1), a substance obtained in five steps from acrolein dimer, gave 1,6-anhydro-3,4-dideoxy-β-DL-erythro-hex-3-enopyranose (2). The compound 1,6:3,4-dianhydro-β-DL-allo-hexopyranose (3), obtained from 2, was converted by reaction with aqueous barium hydroxide followed by hydrolysis of the product, to DL-glucose 5. Treatment of 3 with sodium methoxide in methanol followed by acid hydrolysis of the 1,6-anhydro intermediate 6, gave 3-O-methyl-DL-glucose (7). The same intermediate, 6, along with the methyl glycoside 8, could be obtained by the acid-catalyzed reaction of 3 with methanol. Lithium aluminum hydride reacted with 3 to form 1,6-anhydro-3-deoxy-β-DL-ribo-hexopyranose (9), which was hydrolyzed readily to 3-deoxy-DL-ribo-hexopyranose (10).Yields were excellent throughout. All products obtained from the oxirane 3 were those resulting only from trans diaxial opening of the oxirane ring.

Cycloadditionen von Ketenen mit Fulvenen/Cycloadditions of Ketenes with Fulvenes

1983 ◽  
Vol 38 (4) ◽  
pp. 504-515 ◽  
Author(s):  
Willy Friedrichsena ◽  
Tony Debaerdemaeker ◽  
Andreas Böttcher ◽  
Sabine Hahnemann ◽  
Regine Schmidt
Keyword(s):  
Ring Opening ◽  
Sodium Methoxide ◽  
Ring Cleavage ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ring Opening Reaction ◽  
Acid Catalyzed

Fulvenes (1) add ketenes (2) in a [ π 2 + π 2] manner to give bicyclo[3.2.0]heptenes (3). Ring cleavage with sodium methoxide yields dihydrofulvenes (4) which can be deliydrogenated to give fulvenes (5), whereas the acid catalyzed ring opening reaction of 3 leads to fulvenes (6). The structure of 3h has been clarified by X-ray crystallography.

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