(6-acetyloxy-1H-indol-5-yl) acetate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A suspension of 17.2 g of trans-4,5-dibenzyloxy-β-pyrrolidino-2-nitrostyrene (prepared from 3,4-dihydroxytoluene by a modified procedure of U.S. Pat. No. 3,732,245) and 3.4 g of 10% Pd/C catalyst in 200 ml ethyl acetate was shaken at room temperature, under hydrogen atmosphere and at 50 psi, for 5 hours. To this reaction mixture was added a solution of ethyl acetate (100 ml) containing acetic anhydride (24 ml), triethylamine (20 ml) and dimethylaminopyridine (800 mg) which was previously saturated with hydrogen. The resultant mixture was stirred for 30 minutes at room temperature. The catalyst was removed over a layer of Celite and the filtrate was evaporated to give an oily residue to which crushed ice was added. The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI: mp 130°-131° C.; HNMR (300 MHz, DMSO-d6)δ 2.24 (s,6H), 6.42 (s,1H), 7.22 (s,1H), 7.32 (s,1H), 7.39 (m, 1H) 11.22 (s,1H). The catalyst was removed over a layer of Celite the filtrate was evaporated to give an oily residue to which crushed ice was added The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A suspension of 17.2 g of trans-4,5-dibenzyloxy-β-pyrrolidino-2-nitrostyrene (prepared from 3,4-dihydroxytoluene by a modified procedure of U.S. Pat. No. 3,732,245) and 3.4 g of 10% Pd/C catalyst in 200 ml ethyl acetate was shaken at room temperature, under hydrogen atmosphere and at 50 psi, for 5 hours. To this reaction mixture was added a solution of ethyl acetate (100 ml) containing acetic anhydride (24 ml), triethylamine (20 ml) and dimethylaminopyridine (800 mg) which was previously saturated with hydrogen. The resultant mixture was stirred for 30 minutes at room temperature. The catalyst was removed over a layer of Celite and the filtrate was evaporated to give an oily residue to which crushed ice was added. The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI: mp 130°-131° C.; HNMR (300 MHz, DMSO-d6)δ 2.24 (s,6H), 6.42 (s,1H), 7.22 (s,1H), 7.32 (s,1H), 7.39 (m, 1H) 11.22 (s,1H). The catalyst was removed over a layer of Celite the filtrate was evaporated to give an oily residue to which crushed ice was added The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A suspension of 17.2 g of trans-4,5-dibenzyloxy-β-pyrrolidino-2-nitrostyrene (prepared from 3,4-dihydroxytoluene by a modified procedure of U.S. Pat. No. 3,732,245) and 3.4 g of 10% Pd/C catalyst in 200 ml ethyl acetate was shaken at room temperature, under hydrogen atmosphere and at 50 psi, for 5 hours. To this reaction mixture was added a solution of ethyl acetate (100 ml) containing acetic anhydride (24 ml), triethylamine (20 ml) and dimethylaminopyridine (800 mg) which was previously saturated with hydrogen. The resultant mixture was stirred for 30 minutes at room temperature. The catalyst was removed over a layer of Celite and the filtrate was evaporated to give an oily residue to which crushed ice was added. The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI: mp 130°-131° C.; HNMR (300 MHz, DMSO-d6)δ 2.24 (s,6H), 6.42 (s,1H), 7.22 (s,1H), 7.32 (s,1H), 7.39 (m, 1H) 11.22 (s,1H). The catalyst was removed over a layer of Celite the filtrate was evaporated to give an oily residue to which crushed ice was added The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: At the completion of the reaction, which will generally require from about 30 minutes to about 3 hours, preferably from about 45 minutes to about 2 hours, the reaction system may be acidified to a pH of about 5 or less, preferably about 4.5, by the addition of acetic acid. The reaction mixture is then extracted, preferably after filtration, with ether or dichloromethane one or more times, under a nitrogen gas atmosphere, to recover the product 5,6-dihydroxyindole. According to a particular feature of the invention, the isolated yield of 5,6-dihydroxyindole can be further increased by carrying out the isolation of the product 5,6-dihydroxyindole by adding to the acetic acid mixture a compound which will protect the hydroxy groups to give the product compound in a form which is more stable in air. For example, addition of acetic anhydride to the filtered mixture gives 5,6-diacetoxyindole on heating. It is also possible to form the borate ester ##STR8## by addition of boric acid to the acetic acid reaction mixture. Generally, any protecting group which is stable to acetic acid can be added to the filtered reaction mixture to give the protected 5,6-dihydroxyindole. on heating can be added to the filtered reaction mixture

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a first stage, 5,6-diacetoxyindole and 5,6-dibenzyloxyindole are prepared by means of a cyclizing reduction. In the case of 5,6-dibenzyloxyindole the cyclizing reduction is carried out using iron in the presence of acetic acid. In a second stage, 5,6-dihydroxyindole is obtained:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a first stage, 5,6-diacetoxyindole and 5,6-dibenzyloxyindole are prepared by means of a cyclizing reduction. In the case of 5,6-dibenzyloxyindole the cyclizing reduction is carried out using iron in the presence of acetic acid. In a second stage, 5,6-dihydroxyindole is obtained:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a first stage, 5,6-diacetoxyindole and 5,6-dibenzyloxyindole are prepared by means of a cyclizing reduction. In the case of 5,6-dibenzyloxyindole the cyclizing reduction is carried out using iron in the presence of acetic acid. In a second stage, 5,6-dihydroxyindole is obtained:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: In a first stage, 5,6-diacetoxyindole and 5,6-dibenzyloxyindole are prepared by means of a cyclizing reduction. In the case of 5,6-dibenzyloxyindole the cyclizing reduction is carried out using iron in the presence of acetic acid. In a second stage, 5,6-dihydroxyindole is obtained:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A suspension of 17.2 g of trans-4,5-dibenzyloxy-β-pyrrolidino-2-nitrostyrene (prepared from 3,4-dihydroxytoluene by a modified procedure of U.S. Pat. No. 3,732,245) and 3.4 g of 10% Pd/C catalyst in 200 ml ethyl acetate was shaken at room temperature, under hydrogen atmosphere and at 50 psi, for 5 hours. To this reaction mixture was added a solution of ethyl acetate (100 ml) containing acetic anhydride (24 ml), triethylamine (20 ml) and dimethylaminopyridine (800 mg) which was previously saturated with hydrogen. The resultant mixture was stirred for 30 minutes at room temperature. The catalyst was removed over a layer of Celite and the filtrate was evaporated to give an oily residue to which crushed ice was added. The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI: mp 130°-131° C.; HNMR (300 MHz, DMSO-d6)δ 2.24 (s,6H), 6.42 (s,1H), 7.22 (s,1H), 7.32 (s,1H), 7.39 (m, 1H) 11.22 (s,1H). The catalyst was removed over a layer of Celite the filtrate was evaporated to give an oily residue to which crushed ice was added The resulting white precipitate was collected by filtration to give 6.08 g (65%) of DAI