THE PREPARATION OF THE HYDROXYSKATOLES AND 5,6-DIHYDROXYSKATOLE

Abstract

A new procedure for the preparation of the hydroxyskatoles has been devised. 4-, 5-, 6-, and 7-benzyloxyindole-3-carboxaldehyde and 5,6-dibenzyloxyindole-3-carboxaldehyde have been prepared and give the corresponding benzyloxyskatoles on reduction with either LiAlH4 or NaBH4/Pd–C. The 4-, 5-, 6-, and 7-hydroxyskatoles and 5,6-dihydroxyskatole are readily obtained on catalytic debenzylation of the relevant benzyloxy compound. An alternative method for the preparation of the hydroxyskatoles involving hydrogenolysis of the benzyloxygramines is also described.The possible structures of by-products obtained in some instances are discussed.