1.1- dichloro-3,5-dioxo-4-methyl

Dichloro-3,5-dioxo-2-methyl-4-propyl- E12b, 536 (H3C-CO-A-CO-CH2-R + TeCl4)... 

Methyl 2,3-diamino-6-methylbenzoate gave methyl 6-methyl-2,3-dioxo-l,2,3,4-tetrahydro-5-quinoxalinecarboxylate (252) [(C02H)2,4M HCl, reflux, 90 min 69% note survival of the ester grouping]. 2,3-Diamino-5,6-dichlorotoluene gave 6,7-dichloro-5-methyl-2,3(l//,4//)-quinoxalinedione (253) [(C02H)2, 4M HCl, reflux, 6 h 66%], 2-Isopropylaminoaniline gave l-isopropyl-2,3(l//,4//)-quinoxalinedione (254)... 

Methyl 6-methyl-7-nitro-2,3-dioxo-1,2,3,4-tetrahydro-5-quinoxalinecarboxylate gave methyl 2,3-dichloro-6-methyl-7-nitro-5-quinoxalinecarboxylate (27)... 

Methyl (9,V,12S)-12-[(Benzyloxycarbonyl)(niethyl)aniino]-5-bromo-16,17-dichloro-7-niethoxy-10-niethyl-4,11-dioxo-2-oxa-10-azatricyclo[12.2.2.r, 7]nonadeca-l(16),3(19),5,14,17-pentaene-9-carboxylate (15) [l6 A soln of 14 (8.0 g, 10.7 mmol) in MeOH (5.5 L) at 4 °C was treated with TTN (14.3 g, 32.2 mmol). The mixture was stirred at 4 °C for 18 h. Pyridine (15 mL) was added, and the mixture was concentrated in vacuo. The residue was diluted with brine and extracted with EtOAc. The combined organic layers were washed with sat. aq Na2S203 and brine, dried (MgS04), and concentrated in vacuo. Chromatography (silica gel, hexane/EtOAc gradient 3 1—1 1) afforded 15 as a colorless, amorphous mass yield 380 mg (5%) [a]D29 —120.6 (c 0.45, CHC13) and 16 as a colorless, amorphous mass yield 1.0 g (14%) [a]D29 -170.8 (c 0.69, CHC13). 

Wen found that A-sulfamoyloxamic acid (12), a by-product formed during the permanganate oxidation of 2,1,3-benzothiadiazole (Section II,A,1), can be converted into 3,4-dichloro-l,2,5-thiadiazole-1,1-dioxide (53) by reaction with phosphorus pentachloride. Other thiadiazole-1,1-dioxides that were derived from 12 by methylation of its disilver salt include 2-methyl-3-oxo-4-methoxy-l,2,5-thiadia-zoline-1,1-dioxide (54) and 2,5-dimethyl-3,4-dioxo-l,2,5-thiadia-zolidine-1,1-dioxide (55). 

The following alkoxypyrazines have been prepared from the corresponding dichloropyrazines and alkoxide ions 2,3-dimethoxy-5,6-dimethyl(and diphenyl) (797) 2,3-dibenzyloxy (sodium benzyl oxide in benzyl alcohol at reflux for 24 hours (883)] [but 23-dichloropyrazine with sodium hydride and benzyl alcohol in xylene gave l,4-dibenzyl-2,3-dioxo-l,2,3,4-tetrahydropyrazine)(988)] 2-chloro-5-methoxy (838) 2,5-diethoxy-3,6-dimethyl (872) 2methanolic sodium methoxide refluxed for 2 h) 2,5-dimethoxy-3-phenyl (817) 2-chloro-5-methoxy(and ethoxy)-3,6-diphenyl (817) 2,5-dimethoxy-3,6-dimethyl (and diisopropyl) (844) 2,5-dimethoxy-3-isopropyl-6-methyl (methanolic potassium methoxide at reflux for 6 days) (844) 2(5)-s-butyl-3-chloro-6-ethoxy-5(2)-isobutyl (93) 2-chloro-6-methoxy (838, 883) 2,6-dimethoxy (reflux for 8h) (832) 2,6-diethoxy (reflux for 14 h) (883) 2-benzyloxy-6-chloro (1 equiv. of sodium hydride and benzyl alcohol in benzene at reflux) (832) 2,6-dibenzyloxy (5 equiv. of sodium benzyloxide in benzene at reflux gave 70%) (832) and 3,5-dimethoxy-2-methyl (535). 

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