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Chapter – 1 Preparation and Yield optimization.....
1.4 EXPERIMENTAL
1.4.1 PREPARATION OF 2 – METHYL INDOLINE
STEP – 1 PREPARATION OF ACETONE PHENYL HYDRAZONE
25 ml of phenyl hydrazine was added drop wise to a magnetically
stirred solution of 20 ml of acetone. After the completion of the addition, 5 ml
of acetone was added to the reaction mixture and the reaction mixture was
heated on the water bath to remove the excess of the acetone. Afterwards the
reaction mixture was cooled to room temperature and it was made anhydrous
by means of anhydrous sodium sulphate or anhydrous calcium chloride. The
solution was filtered to give the dark yellow solution of phenyl hydrazone.
Yield - 80 %, BP - 140-142°C (141-142°C b )
STEP – 2 PREPARATION OF 2-METHYL INDOLE
30 gm of acetone phenyl hydrazone was added drop wise to a beaker
containing 75 gm of polyphosphoric acid with constant stirring. The reaction
mixture was heated on water bath for 2-3 hours, where the orange coloured
solution became dark red-brown. After that the temperature of the reaction
mixture was raised to 120°C and then it was cooled to room temperature.
After that 400 ml of distilled water was added to the reaction mixture to
decompose the polyphosphoric acid, the whole content was steam distilled to
acquire the 2-Methyl Indole as white coloured shining crystals. Yield - 79 %,
MP - 58-59°C (56-57°C c )
STEP – 3 PREPARATION OF 2-METHYL INDOLINE
METHOD – (A)
0.05 mole 2-methyl indole was dissolved in 110 ml of trifluoroacetic
acid under nitrogen atmosphere. The solution was cooled in an ice bath and
90 ml of about 1 M BH3.THF in tetrahydrofuran solution was added slowly
b H. M. Kissman, D. W. Farnsworth and B. Witkop; J. Am. Chem. Soc., 1952, 74, 3948.
c C. F. H. Allen and J. Vanallan; Organic Syntheses, 1955, Coll. Vol. 3, p. 597.
Department of Chemistry, Saurashtra University, Rajkot-360 005 40