GB1118718A - Process for preparing derivatives of t-butyl ª‡-(3-indolyl)-acetate - Google Patents

Abstract

Compounds of the formula <FORM:1118718/C2/1> wherein R1 is hydrogen or C1- 5 alkyl and R2 is a C1- 5 alkoxy radical, are obtained by reacting at least two moles of hydrogen chloride with a phenylhydrazine sulphonate of formula <FORM:1118718/C2/2> wherein M is alkali metal, in t-butanol at 20-55 DEG C. for 10-50 hours and reacting the phenylhydrazine hydrochloride formed of the formula <FORM:1118718/C2/3> without isolating it with a t-butyl levulinate of formula CH3COCH2CHR1-COOC(CH3)3 at temperature of from 70 DEG C. to reflux for 4-7 hours, the process being effected in the presence of 0-20 moles of water per mole of sulphonate. The reaction is preferably effected under an inert atmosphere and the reaction between the phenylhydrazine hydrochloride and the t-butyl levulinate is preferably carried out at a pH of 3-4, which may be adjusted by the addition of concentrated base, e.g. ammonium hydroxide. The hydrogen chloride may be employed in the form of hydrochloric acid or hydrogen chloride may be bubbled through the mixture. The products may be converted to 1-aroyl or 1-heteroaroyl derivatives, e.g. t-butyl-2-methyl-5-methoxy-3-indolyl acetate is treated with sodium hydride and p-chlorobenzoyl chloride followed by pyrolysis to give a -(1-p-chlorobenzoyl)-2-methyl -5-methoxy-3-indolyl acetic acid; the corresponding 5-ethoxy derivative may be obtained in a similar manner.