3-Oxo-3,4-dihydro- -1-oxid

Oxo-3,4-dihydro-2-quinoxalinecarbonitrile 1-oxide gave 3-chloro-2-quinoxa-linecarbonitrile 1-oxide (22) (POCI3, Me2NCHO, PhMe, reflux, 2 h 45%). °... 

Methyl-3-oxo-3,4-dihydro-2-quinoxalinecarbonitrile 1-oxide (149) gave 6-methyl-... 

Ethyl 3-oxo-3,4-dihydro-2-quinoxalinecarboxylate Ethyl 6-oxo-4,6-dihydro-5-quinoxalonecarboxylate Ethyl 3-oxo-3,4-dihydro-2-quinoxalinecarboxylate 1-oxide... 

Methyl-3-oxo-3,4-dihydro-2-quinoxalinecarbonitrile 1-oxide (149) gave 6-methyl-2(lfl)-quinoxalinone (150) (Na2S204, H20, EtOH, °C, h %).98... 

Hydroxy-3-oxo-3,4-dihydro-2-quinoxalinecarbonitrile 4-Hydroxy-3-oxo-3,4-dihydro-2-quinoxalinecarbonitrile 1-oxide 4-Hydroxy-3-oxo-3,4-dihydro-2-quinoxalinecarboxylic acid 1 -Hydroxy-3-phenyl-2( l/f)-quinoxalinone... 

Methyl 5-methoxy-6,7-dimethyl-3-oxo-3,4-dihydro-2-quinoxalinecarboxylate Methyl 5-methoxy-6,7-dimethyl-3-oxo-3,4-dihydro-2-quinoxalinecarboxylate 1 -oxide Methyl 3-methoxy-2-quinoxalinecarboxylate 2-Methy l-3-( 1 -methylallyl)quinoxaline 2-Methyl-3-(2-methylallyl)quinoxaline 2-Methyl-3-methylaminomethylquinoxaline 5-Methyl-7-methylamino-8-nitro-2-phenylquinoxaline 5-Methyl-7-methylamino-8-nitro-3-phenylquinoxaline... 

Methyl 3-chloroformyl-2-pyrazinecarboxylate Methyl 6-chloro-5-methoxy-3-oxo-3,4-dihydro-2-pyrazinecarboxylate Methyl 6-chloro-3-methoxy-2-pyrazinecarboxylate Methyl 3-chloro-5-methyl-2-pyrazinecarboxylate Methyl 5-chloro-6-methyl-2-pyrazinecarboxylate Methyl 5-chloro-6-methyl-2-pyrazinecarboxylate 1-oxide Methyl 6-chloro-3-nitro-2-pyrazinecarboxylate Methyl 6-chloro-3-oxo-3,4-dihdyro-2-pyrazinecarboxylate... 

Reaction of the amides (267a,b) with SOCl2 gave the 4-oxo-3,4-dihydro-l-benzopyrano[2,3-c]-1,2,6-thiadiazine 2-oxides (268a,b) in 83% and 90% yield, respectively <79CB1012>. 

Methyl-l -(1 -oxo-2-nitro-ethyl)-E16d, 244 (En-Oxid.) 4-Nitro-l-propanoyl- VII/2a, 675 2H-l,3-Benzoxazin 8-Methoxy-2-oxo-3.4-dihydro- E4, 204 (2-OH — Ar — CH2 — NR2 + Harnstoff)... 

Ethyl 1-hydroxymethyl- (131) was oxidized to ethyl 1-formyl-5,7-dimethyl-4-oxo-3,4-dihydro-6-phthalazinecarboxylate (132) (substrate, iV-bromosuccini-... 

Oxidation of 8-( 1 -methylethenyl)-2-oxo-7-thia-1 -azabicyclo[4.3.0]octa-3,5-diene-5,8-dicarboxylate (104) and its 3,4-dihydro derivative in CHCI3 with peracids (w-chloroperbenzoic acid and CF3CO3H) at room temperature gave diethyl 3-methyl-6-oxo-2/7,6//-pyrido[2,l-Z)][l,3]thiazine-4,9-dicarboxylate and its 7,8-dihydro derivative in 66% and 56% yield, respectively (99JCS(P1)3569). 

Only one procedure has been reported recently within this category. Thus 7-chloro-l-methyl-5-phenyl-2,3-dihydro-lH-benzodiazepin-2-one 4-oxide (437) with dimethyl acetylenedicarboxylate in methylene chloride at 20° C for 3 days gave a separable mixmre of the primary tricyclic adduct, dimethyl lO-chloro-6-oxo-llb-phenyl-5,6,7, 1 lb-tetrahydroisoxazolo[2,3-t/] [ l,4]benzodiazepine-1,2-dicarboxylate (438), and its rearrangement product, 6-chloro-4-(2-methoxalyl-2-methoxycarbonyl-l-phenylvinyl)-l-methyl-3,4-dihydro-2(lT0-quinoxalinone (439) each product afforded 6-chloro-l-methyl-2(l//)-quinoxalinone (440) on refluxing in ethanol (see also Section 1.7.13). However, the final quinoxaline (440) was best obtained in 75% yield) by simply heating the initial substrate (437) and dimethyl... 

With respect to using methyl viologen as electron relay, it might be of interest to note tlmt MV " can be oxidized by positive holes produced in illuminated colloidal semiconductors such as Ti02 Two oxidation products of MV are 1, 2 -di-hydro-l,r-dimethyl-2 -oxo-4,4 -bipyridylium chloride and 3,4-dihydro-l,r-dime-thyl-3-oxo-4,4 -bipyridylium chloride, which can readily be detected by their strong fluorescences at 516 nm and 528 nm, respectively. These products are also produced in the direct photolysis of MV " solutions and in the reaction of MV "" with OH radicals in homogeneous solution... 

Hydrogen peroxide converts morpholine into its 4-hydroxy derivative (50JA2280), but TV-alkyl morpholines yield 3-oxo compounds if ruthenium(VIII) oxide or sodium metaperiodate are used as oxidants (76S598). Chlorine at -70 °C oxidizes the thiomorpholine (116) to the dihydro-1,4-thiazine (117) (73JCS(Pl)l32l), but more vigorous conditions result in the formation of S-oxides. 

A relatively large number of papers has described the preparation of oxo derivatives of 3,4-dihydro-2//-1,3-oxazine. The previously reported1 use of diketene as a cyclizing agent has found wider application. Gunar et al.1 described the reaction of diketene with ammonium thiocyanate. It passes through an intermediate acetoacetyl isothiocyanate to a 2-thiono derivative, which, on oxidation, yields 50 [Eq. (37)]. 

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