Triphenylphosphine → 3-Cyclopropyl-5,6,10,11-tetrahydro-8-methyl-benzo[g]pyrazino[1,2-a]indole fumarate

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Reaction Conditions

Reaction Steps

Trifluoromethanesulphonic acid 5,6,10,11-tetrahydro-8-methyl-benzo[g]pyrazino[1,2-a]indol-3-yl-ester (2.0 g), 1.85 g of anhydrous lithium chloride, 0.44 g of bis(triphenylphosphine)palladium dichloride, 0.88 g of triphenylphosphine and 3.5 g of tri-n-butyl-cyclopropyltin were suspended in 25 ml of dimethylformamide under argon and heated to 120° C. for 6 h. while stirring. The reaction mixture was added to 500 ml of water and extracted once with 200 ml of ethyl acetate and twice with 100 ml of ethyl acetate each time. The ethyl acetate extracts were extracted four times with 2N hydrochloric acid (1×100 ml, 3×50 ml), the aqueous phases were combined, made basic with 120 ml of 28% sodium hydroxide solution and extracted three times with 100 ml of methylene chloride each time. The combined methylene chloride extracts were washed twice with 60 ml of saturated potassium fluoride solution each time and once with 500 ml of water. The organic phase was dried with MgSO4 and freed from solvent. The residue, 1.1 g of brown oil, was chromatographed on 60 g of aluminium oxide (neutral, III) with methylene chloride as the eluent. There was obtained 0.67 g of crude product which was again chromato-graphed on 8 g of silica gel with methylene chloride/methanol mixtures (50:1 to 20:1). The product, 0.14 g of brown oil, was dissolved in a 10-fold amount of ethanol and treated with 1.1 equivalents of a saturated solution of fumaric acid in ethanol. After concentration to a volume of about 1 ml and addition of 3 ml of ethyl acetate there separated 0.11 g of brown crystals which were recrystallized from 4 ml of isopropanol. There were obtained 50 mg (4%) of 3-cyclopropyl-5,6,10,11-tetrahydro-8-methyl-benzo[g]pyrazino[1,2-a]indole fumarate (1:1); m.pt.: 184°-187° C. (dec.).

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