tert-butyl 6,8-dioxo-2,5-diazaspiro[3.5]nonane-2-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 6,8-Dioxo-2,5-diaza-spiro[3.5]nonane-2,7-dicarboxylic acid 2-tert-butyl ester 7-methyl ester (1.1 g; 3.5 mmol) is refluxed in acetonitrile/water (18 ml/2 ml) for 50 minutes and evaporated to dryness. The residue is triturated with CH2Cl2 to deliver the title compound as colorless crystals. 1H-NMR (400 MHz; DMSO-d6): Keto-enol tautomerism. 10.70 (s, 1H); 8.75 (s, 0.5H); 7.55 (s, 0.5H); 4.85 (s, 1H); 3.94 (bd, 2H); 3.86 (bd, 2H); 3.78 (bs (2H); 1.40 (s, 9H); MS (m/z) ES+: 255 (25; MH+); 199 (100). evaporated to dryness The residue is triturated with CH2Cl2