Hydrochloric Acid → (+)-(1r)-2-Pentyl-2-cyclopenten-1-ol

Participants

Reaction Steps

A solution of 2-pentyl-2-cyclopenten-1-one (9.12 g, 60 mmole) in 140 ml of tetrahydrofurane (THF) was treated with an oxazaborolidine represented above, namely (S)-tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c][1,3,2]oxazaborole (16.7 ml; 0.36 M in toluene, 6.0 mmole; see D. J. Mathre, ref. cited). A solution of BH3.S(CH3)2 (3.30 ml=2.64 g, 34.8 mmole) in THF (60 ml) was added dropwise at 0° over 1 h. The reaction was stopped with 3 ml of methanol (development of H2), followed by ethyl ether and 5% HCl. The organic phase, which had been washed to neutrality (2× with water and 1× with brine), was separated and the solvent evaporated. 9.5 g of a crude product were obtained, which was distilled in a bulb-to-bulb apparatus (oven temp. 60°/11 Pa), to give 8.1 g of (+)-(1R)-2-pentyl-2-cyclopenten-1-ol (yield 89%).

Provenance & Evidence