4-Formylbenzoic acid → 4-[3-oxo-3-((1aS,5aR)-1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalen-4-yl)-propenyl]-benzoic acid

Participants

Reaction Steps

A solution of 4-formyl-benzoic acid (1.04 g mg, 6.93 mmol), (1aS,5aR)-1-(1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalen-4-yl)-ethanone (850 mg, 3.86 mmol), NaOMe (4.17 g, 77.2 mmol) in methanol (30 mL) is stirred at 65° C. for 2 h. Another portion of 4-formyl-benzoic acid (400 mg, 2.66 mmol) is added and stirring is continued at 65° C. for 2 h. The reaction mixture is diluted with diethyl ether (200 mL) and washed with 5% aq. citric acid solution followed by water. The organic phase is dried over MgSO4 and evaporated. The crude product is purified by CC on silica gel eluting with DCM containing 2-7% methanol, followed by crystallisation from methanol:water 1:1 to give 4-[3-oxo-3-((1aS,5aR)-1,1,2-trimethyl-1,1a,5,5a-tetrahydro-3-thia-cyclopropa[a]pentalen-4-yl)-propenyl]-benzoic acid (780 mg) as beige yellow powder; LC-MS: tR=1.06 min, [M+1]+=353.03; 1H NMR (CDCl3): δ 8.13 (d, J=8.2 Hz, 2H), 7.76 (d, J=15.2 Hz, 1H), 7.68 (d, J=8.2 Hz, 2H), 7.29 8d, J=15.8 Hz, 1H), 3.14 (dd, J=5.9, 18.8 Hz, 1H), 2.96 (d, J=18.8 Hz, 1H), 2.44 (s, 3H), 2.00-1.91 (m, 2H), 1.15 (s, 3H), 0.75 (s, 3H).

Provenance & Evidence