1,1,3,3-Tetraethoxy-2-methylpropane → 6-methyl-1H,3H-2,4,7a,8-tetraaza-cyclopenta[a]indene-2-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

A mixture of 3-amino-2,6-dihydro-4H-pyrrolo[3,4-c]pyrazole-5-carboxylic acid tert-butyl ester (5 g; 22.3 mmol; 1 eq.) and 1,1,3,3-tetraethoxy-2-methylpropane (4.32 mL; 22.3 mmol; 1 eq.) in AcOH (50 mL) was stirred at 50° C. for 20 hours then diluted with water (250 mL). The precipitate was filtered off and dried to afford the title compound (3.5 g, 57%) as a pale beige solid. 1H NMR (DMSO-d6) δ 8.98-8.95 (m, 1H), 8.43 (d, J=2.1 Hz, 1H), 4.61-4.54 (m, 4H), 2.31 (s, 3H), 1.47 (s, 9H). HPLC (max plot) 99.7%; Rt 3.27 min. UPLC/MS: (MS+) 275.0 ([M+H]+).

Provenance & Evidence