The t-Butyloxycarbonyl (BOC) group on indoles and pyrroles can be removed cleanly and in high yield by simple thermolysis: no acid, no base, no solvent is required.
In recent years considerable attention has been given to the problem of finding suitable protecting groups for indoles and pyrroles.2 The r-butyloxycarbonyl (BOC) group, though not resistant to strong acids or bases, has, nevertheless, proven to be extremely useful since it directs lithiation a to the indole and pyrrole nitrogens at low temperature (-78"C).3 Our work on the synthesis of the antitumor agent CC-1065 offered us the opportunity to explore the reactivity of this group, and we report here a procedure for removing it in excellent yield.
To introduce the BOC group we used the remarkably mild conditions of Grehn and RagnarssonP
We found, however, that yields were improved appreciably (lo-20%) by using a simplified workup procedure. Thus, after all starting material had been consumed (TLC), the solvent was removed and the residue was purified directly by silica gel flash chromatography (typically, CH2C12:hexanes, 1: 1 to 10: l),