Protection of Carbonyl Compounds
3165
Typical Procedure for the Rapid Preparation of Benzalazine
Hydrazinium monoformate was prepared by carefully neutralizing equal
quantities of hydrazine hydrate (99–100%) and formic acid (85%) below
08C, with constant stirring. To this neutral solution (15 mL) in a 500-mL
round-bottomed flask, 0.1 mol of benzaldehyde (10.6 g) was added while
stirring at 258C. An exothermic reaction affords the yellow solid in 30 s,
which was filtered and recrystallized from ethanol to get 10.2 g of benzalazine
crystals (ꢀ98%).
Typical Experimental Procedure for the Regeneration of
3-Nitrobezaldehyde from 3,30-Dinitrobenzalazine
3,30-Dinitrobenzalazine (1.49 g, 5 mmol) is added to a rapidly stirred solution
of triethylammonium chlorochromate (4 g) in dichloroethane (20 mL). The
resultant dark mixture is stirred for 1 h, and the reaction mixture quenched
by ether (25 mL) and filtered through a bed of celite. Removal of solvent
and silica-gel chromatography gave 3-nitrobenzaldehyde (1.23 g, 82%), mp:
42–438C. IR (KBr): 3050 (m), 2950 (m), 2760 (m), 1685 (s), 1610 (m),
1
1570 (m), 1360 (m), 828 (m), 760 (m) cm21; H NMR (d): 9.7 (s, 2H),
8.0–8.4 (m, 8H). MS (m/z): 151 (Mþ).
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