1-Dimethylsulfamoyl-2-t-butyldimethylsilyl-5-imidazolecarboxaldehyde → 2-(tert-Butyldimethylsilyl)-N,N-dimethyl-1H-imidazole-1-sulfonamide

To 2-amino-4-nitrophenol (1) (4.00 g, 25.95 mmol), triethylamine (15.20 mL, 109.0 mmol) and 4-dimethylaminopyridine (0.063 g, 0.52 mmol) slurried in anhydrous CH2Cl2 (250 mL) at 0° C. under argon added chloroacetyl chloride (2.27 mL, 28.55 mmol) via syringe. After refluxing for 72 h pure product was filtered off and washed with water. The mother liquor was washed successively with phosphoric acid (0.5M), saturated sodium bicarbonate, water and brine and then dried over MgSO4. This solution was adhered to silica and purified by flash chromatography on silica with hexane/ethyl acetate (4:6) to give additional product. The combined solids were dried in vacuo to give pure 6-nitro4H-benzo[1,4]oxazin-3-one (2) (4.12 g) in 82% yield. To a slurry of (2) (1.49 g, 7.65 mmol) in anhydrous THF (40 mL) under argon in a 2-neck round-bottom flask equipped with a reflux condenser was added borane-dimethyl sulfide complex (15.3 mL, 30.62 mmol). The mixture was heated at reflux until starting material was no longer observed via thin layer chromatography (2 h). The reaction mixture was cooled to rt and carefully quenched by the dropwise addition of methanol. The resulting mixture was then refluxed an additional 10 minutes. The crude reaction mixture was concentrated in vacuo and purified by flash chromatography on silica with hexane/ethyl acetate (8:2) to give pure 6-nitro-3,4-dihydro-2H-benzo[1,4]oxazine (3) (1.36 g) as an orange solid in 99% yield. To (3) (0.032 g, 0.178 mmol) and formalin (37% in H2O, 0.20 mL, 2.67 mmol) in anhydrous acetonitrile (1.5 mL) at ambient temperature was added sodium cyanoborohydride (0.034 g, 0.534 mmol). This solution was stirred for 30 min before adding glacial acetic acid (0.032 mL, 0.534 mmol). The resulting mixture was stirred an additional 16 h. The organics were taken up in diethyl ether and washed successively with NaOH (2N) and brine, dried over MgSO4 and concentrated in vacuo. The resulting solids were purified by flash chromatography on silica with hexane/ethyl acetate (7:3) to give pure 4-methyl-6-nitro-3,4-dihydro-2H-benzo[1,4]oxazine (4) (0.031 g) in 93% yield. To (4) (2.16 g, 11.12 mmol) and 10% palladium on carbon (0.216 g, 10 wt. %) under argon was added methanol (MeOH) (30 mL) followed by THF (30 mL). Hydrogen was bubbled thru the resulting slurry until no (4) remained visible by thin layer chromatography (2 h). Celite was added and the mixture was filtered through a bed of celite followed by a MeOH wash. The resulting solution was concentrated in vacuo to give pure 4-methyl-3,4-dihydro-2H-benzo[1,4]oxazin-6-ylamine (5) (1.86 g) as a pale purple oil in 100% yield which was carried on without further purification. To (5) (1.86 g, 11.34 mmol) and imnidazoline-2-sulfonic acid (1.84 g, 12.24 mmol) in anhydrous acetonitrile (50 mL) under argon at 0° C. was added triethylamine (3.26 mL, 23.36 mmol). This solution was gradually warmed to ambient temperature and stirred for 16 h. At that time an additional amount of imidazoline-2-sulfonic acid (0.86 g, 5.55 mmol) was added and the resulting mixture was stirred an additional 5 h. This solution was concentrated in vacuo and the residues were taken up in H2O. The organics were extracted into CH2Cl2 and washed twice with NaOH and then brine, dried over MgSO4 and concentrated in vacuo. The resulting foam was purified by flash chromatography on silica with 20% methanol (saturated with ammonia) in chloroform to give pure imidazolidin-2-ylidene-(4-methyl-3,4-dihydro-2H-benzo[1,4]oxazin-6-yl)amine (6) (E-1) (0.905 g) in 34% yield.