Hydrochloric Acid → 1-cyclopentyl-1H-pyrazole

A mixture of 1,1,3,3-tetramethoxy-propane (13.6 g, 83 mmol) and 1-cyclopentylhydrazine-2-carboxylic acid tert-butyl ester from Ex B18 (16.6 g, 83 mmol) in water (150 mL) was treated with conc HCl (21 mL, 252 mmol) and the resulting mixture was heated at reflux overnight. The reaction mixture was allowed to cool to RT and was extracted with ether. The extracts were washed with brine, dried over anhydrous MgSO4 and filtered. The filtrate was concentrated in vacuo to give 1-cyclopentyl-1H-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+]

1. temperaturethe resulting mixture was heated
2. temperatureat reflux overnight
3. extractionwas extracted with ether
4. washThe extracts were washed with brine
5. dry with materialdried over anhydrous MgSO4
6. filtrationfiltered
7. concentrationThe filtrate was concentrated in vacuo

ORD record

ord-a05c708e2a44488e92bbbf8a814ced04

Source dataset

uspto-grants-2012_03

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08143293B2