3,6 -dihydropyrazine 1,4-dioxide

Although hexamethyl-2,3-dihydropyrazine 1,4-dioxide (166) does not exhibit typical nitrone properties, oxaziridines are nevertheless formed on photolysis with light of wavelength greater than 300 nm, only the monooxaziridine (167) is formed, whereas with light of wavelength down to 200 nm, cis- (168) and trans- (169) dioxaziridines are obtained.148... 

Bis(hydroxyamino)-2,3-dimethylbutane (160) and glyoxal gave 2,2,3,3-tetramethyl-2,3-dihydropyrazine 1,4-dioxide (161) (H20—EtOH, reflux, 10 min 83% naturally not subject to facile oxidation).702 Also other examples.1,86 237 414,466,483 588 988 1108... 

Tetramethyl-2,3-dihydropyrazine 1,4-dioxide (303) gave 2,2,3,3-tetram-ethyl-l,4-piperazinediol (304) (NaBH4, H20, 20°C, 24 h 81% homologues likewise).702 Also analogous reductions.702... 

Dihydropyrazine 1,4-dioxides have been reported by Lamchen and Mittag... 

Reduction of 2,2,3,3,5,6-hexamethyl-2,3-dihydropyrazine 1,4-dioxide (78) with sodium borohydride gave l,4-dihydroxy-2,2,3,3,5,6-hexamethylpiperazine (555) and attempted deoxygenation of (78) by zinc and hydrochloric acid gave the bishydroxylamine (79) (555). Compound (78) did not form benzylidene derivatives with benzaldehyde (555) and it was only slowly attacked by selenium dioxide one equivalent of selenium dioxide required 5 days boiling under reflux before the nitrone was completely reacted, and the product was thought to be 6-formyl-... 

The photochemical isomerization of hexamethyl-2,3-dihydropyrazine 1,4-dioxide has been investigated (1606). 

The reactions of 2,5-dimethyl-3,6-diphenyl-2,5-dihydropyrazine 1,4-dioxide and 3,6-diphenyl-2,5-dihydropyrazine 1,4-dioxide with acetic anhydride and a small amount of sulfuric acid afforded 2,5-dimethyl-3,6-diphenylpyrazine 1-oxide and... 

One of the most common approaches to pyrazine ring construction is the condensation of diaminoethane and 1,2-dicarbonyI compounds such as 206 to provide pyrazines 207 after aromatization. Aromatization was accomplished by treating the dihydropyrazines with manganese dioxide in the presence of potassium hydroxide <00JCS(P1)381>. The N-protected 1,2-dicarbonyl compounds 206 were prepared from L-amino acids by initial conversion into diazoketones followed by oxidation to the glyoxal. 

Condensation of 1,2-bishydroxylamines (84) with 1,2-dicarbonyl compounds leads to derivatives of 2,3-dihydropyrazine-l,4-dioxides (85) (255), whereas the reaction with ninhydrin gives [1,2-b] pyrazine N,N -dioxides (86) (Scheme 2.32)... 

Diisobutyl-3-methoxypyrazine 1,4-dioxide with phosphorus trichloride in ethyl acetate at 40° gave 2,5-diisobutyl-3-methoxypyrazine (and 2,5-diisobutyl-4-methoxy-3-oxo-3,4-dihydropyrazine 1-oxide similarly treated gave 3,6-diisobutyl-I-methoxy-2-oxo-l, 2-dihydropyrazine) (see Section 15) (980). 

Cleavage of the Me-0 bond in 3,6-diisobutyl-l-methoxy-2-oxo-l,2-dihydro-pyrazine (93) with methylmagnesium iodide at 150° gave 2-hydroxy-3,6-diisobutyl-pyrazine 1-oxide (94) and the 1,4-dioxide was prepared similarly from 2,5-diisobutyl4-methoxy-3-oxo-3,4-dihydropyrazine 1-oxide and also from 2,5-diisobutyl-3-methoxypyrazine 1,4-dioxide (980). 

Diazomethane methylation of 3-hydroxy-2,5-diisobutylpyrazine 1,4-dioxide has been shown to give the 4-methoxypyrazine 1-oxide, 2,5-diisobutyl4-methoxy-3-0X0-3,4-dihydropyrazine 1-oxide (96) (843, 980) [and some 3-methoxy-2,5-diisobutylpyrazine 1,4-dioxide (4 l)(980)] 5-s-butyl-3-hydroxy-2-isobutylpyrazine... 

Hydroxypyrazine 1 oxide was reduced with hydrogen at atmospheric pressure over Raney nickel to 2-hydroxypyrazine (108) [but failed to react with phosphorus trichloride in chloroform (108)], and 3-hydroxy-2-isobutyl-5-isopropylpyrazine 1,4-dioxide was reduced with hydrogen over nickel to 3-hydroxy-2-isobutyl-5-isopropylpyrazine (740a). 2-(A -Anilino-yV-methylcarbamoyl)-4-methyl-3oxo-3,4-dihydropyrazine 1 oxide with sodium dithionite produced 3-(A -anilino-A -methyl-carbamoyl)- -methyl-2oxo-l, 2-dihydropyrazine (1137). 

Dihydropyrazine-l,4-dioxides (97) have been prepared by reaction of... 

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