Hydrochloric Acid → 1-cyclopentyl-1H-pyrazole

Participants

Reaction Steps

A mixture of 1,1,3,3-tetramethoxypropane (13.6 g, 83 mmol) and N2-cyclopentyl-N1-(tert-butoxycarbonyl)hydrazine (16.6 g, 83 mmol, see Ranatunge et al., J. Med. Chem. (2004), 47, p2180-2193) in water (150 mL) was treated with cone. HCl (21 mL, 252 mmol). The resulting mixture was heated at reflux overnight. The completed reaction mixture was extracted with ether and the extracts were washed with brine, dried over anhydrous MgSO4, and concentrated in vacuo to give 1-cyclopentyl-1 H-pyrazole (8.0 g, 71% yield. 1H NMR (400 MHz, CDCl3): δ 7.52 (s, 1 H), 7.43 (s, 1 H), 6.24 (s, 1 H), 4.68 (m, 1 H), 2.20-1.71 (m, 8 H). MS (ESI) m/z; 137.1 [M+H+].

Provenance & Evidence