ADDITION REACTION;
AROMATIZATION;
ARTICLE;
CHEMICAL STRUCTURE;
CRYSTAL STRUCTURE;
CYCLIZATION;
DEHYDROGENATION;
ELIMINATION REACTION;
PROTON NUCLEAR MAGNETIC RESONANCE;
REDUCTION;
X RAY CRYSTALLOGRAPHY;
† 88%; 6b 265-266 °C, 84%; 6c 240 °C, 80%; 6d 245-246 °C, 82%; 7a 216-218 °C, 80%.
6
34447578301
note
Typical procedure for the synthesis of compounds 6e-f. A mixture of equimolar quantities of 4 and 5e-f was stirred in trifluoroacetic acid at room temperature for 24 h. The solvent was distilled off under reduced pressure, and the residue was recrystallised from ethanol. The product was filtered off, washed with ether and dried in air. Mp, yields: 6e 230-232 °C, 70%; 6f 242-244 °C, 80%.
7
34447552992
note
Typical procedure for the synthesis of compounds 8a-e using ferrous sulfate. 1 mmol of 6 was dissolved in 5 ml of 20% aqueous ammonia, and an aqueous solution of 7 mmol of ferrous sulfate solution was added with stirring. The reaction mixture was refluxed for 5 min. The product was extracted with methanol (3 × 10 ml) and filtered. The residue was washed with water and recrystallised from ethanol. Mp, yields: 8a 288-290 °C, 60%; 8b 272-273 °C, 64%; 8c 173-174 °C, 40%; 8d 80-82 °C, 42%; 8e 170-172 °C, 64%.
8
34447555293
note
Procedure for the synthesis of compound 8b with stannous chloride. A solution of stannous chloride dihydrate (3 mmol) in 2 ml of acetic acid and 0.5 ml of concentrated hydrochloric acid was added to a solution of 6 (1 mmol) in 3 ml of acetic acid. The mixture obtained was stirred for 5 min and the precipitate obtained was filtered off. The product was dissolved in ethanol, and hydrogen sulfide was allowed to pass through the solution until the formation of stannous sulfide was complete. The mixture was filtered and concentrated under reduced pressure, the product was separated, washed with ethanol and dried in air. Yield: 33%.
9
34447568822
note
Typical procedure for the synthesis of compounds 8a,b,d-f with sodium dithionite. A mixture of 1 mmol of 6e and 6 mmol of sodium dithionite in 5-6 ml of 20% ammonia solution was stirred at 60 °C for 30-40 min. The reaction was concentrated under vacuum and kept for 24 h at room temperature. The precipitated product was separated by filtration, washed with water and recrystallised from ethanol. Yields 70-90% (Table 1).
10
34447568823
note
2/Pd. A solution of 6 in DMF was treated with hydrogen (15 atm) in the presence of Pd/C at 50 °C for 2 h. The reaction solution was filtered, and the solvent was distilled off under reduced pressure. The residue was recrystallised from ethanol. Yields 45-68%.
11
34447575320
note
Typical procedure for the synthesis of compounds 11a,b. A mixture of equimolar quantities of 4,10a,b and triethylamine in acetonitrile was kept at room temperature for 24 h. The reaction solution was neutralised with concentrated hydrochloric acid. The precipitated product was filtered off and washed with water and acetonitrile. Yields 75-85%.
12
34447548183
note
Typical procedure for the synthesis of 12a,b. A solution of stannous chloride dihydrate (3 mmol) in 2 ml of acetic acid and 0.5 ml of concentrated hydrochloric acid was added to a solution of 11 (1 mmol) in 3 ml of acetic acid and the reaction mixture was stirred for 5 min. The precipitate was filtered off, dissolved in DMF and purified by thin layer chromatography on alumina oxide with chloroform-ethanol (9:1) as eluent. Mp, yields: 12a 270-272 °C, 30%; 12b >300 °C, 34%.
13
0001301160
RajanBabu T.V., Chenard B.L., and Petti M.A. J. Org. Chem. 51 (1986) 1704
