[C:1]1(=O)[CH2:6][CH2:5][CH2:4][C:3](=[O:7])[CH2:2]1.Cl.[NH:10]([CH2:12][C:13]([O:15][CH2:16][CH3:17])=[O:14])[NH2:11].[CH3:18]OC(N(C)C)OC>CN(C)C=O>[CH2:16]([O:15][C:13](=[O:14])[CH2:12][N:10]1[C:1]2[CH2:6][CH2:5][CH2:4][C:3](=[O:7])[C:2]=2[CH:18]=[N:11]1)[CH3:17]To a solution of cyclohexane-1,3-dione (50.7 g, 45.2 mmol) in N,N-dimethylformamide (700 mL) was added ethyl hydrazinoacetate hydrochloride (70 g, 45.2 mmol). The reaction mixture was stirred for 5 minutes, then dimethoxymethyl-dimethyl-amine (53.9 g, 45.2 mmol) was added. The reaction mixture was divided into 50 vials, which were heated in a microwave at 190° C. for 2 minutes. After cooling to room temperature, the combined reaction mixture was concentrated in vacuo to remove most of N,N-dimethylformamide. Water (200 mL) was added, and the resulting dark brown mixture was extracted with ethyl acetate (200 mL×3). The organic layers were combined, washed with brine (600 mL), dried over sodium sulfate and concentrated in vacuo to afford a brown oil, which was placed in a fridge overnight. The resulting yellow precipitate was filtered and washed with petroleum ether to give (4-oxo-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (79 g, 79%) as yellow crystals. 1H NMR (400 MHz, CDCl3) δ ppm 7.92 (s, 1 H), 4.89 (s, 2 H), 4.26 (m, 2 H), 2.80 (t, J=6.4 Hz, 2 H), 2.51 (t, J=6.4 Hz, 2 H), 2.20 (t, J=6.4 Hz, 2 H), 1.31 (t, J=7.2 Hz, 3 H). MS calcd. for C11H14N2O3 222, obsd. (ESI+) (M+H)+ 223.
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