Lithium Hydroxide → (1aS,5aR)-1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalene-4-carboxylic acid

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Reaction Conditions

Reaction Steps

To a solution of crude (1aS,5aR)-1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalene-4-carboxylic acid ethyl ester (10.3 g, 41.2 mmol) in ethanol (200 mL) a solution of 2N aq. LiOH (300 mL) is added. The resulting mixture is stirred at 70° C. for 1 h, cooled to rt and diluted with water (250 mL). The aq. solution is extracted three times with DCM (125 mL) before it is acidified to pH 3 by adding citric acid. The acidified solution is extracted twice with DCM (2×250 mL), These second extracts are combined, dried over Na2SO4, filtered and evaporated to leave (1aS,5aR)-1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalene-4-carboxylic acid (7.0 g) as a yellow solid. LC-MS: tR=0.95 min, [M+1]+=223.00. 1H NMR (CDCl3): δ 3.04-2.92 (m, 1H), 2.83 (d, J=19.3 Hz, 1H), 2.39 (s, 3H), 1.91-1.87 (m, 2H), 1.13 (s, 3H), 0.73 (s, 3H).

Provenance & Evidence