Diethoxymethyl protected indoles: Synthesis and regioselective transformations

Article abstract of DOI:10.1055/s-1996-4356

Reaction of the indoles 1a-d with triethyl orthoformate gives access to the N-diethoxymethyl derivatives 2a-d. Convenient and mild removal of the diethoxymethyl substituent is possible by subsequent treatment of 2a-d with aqueous HCl and NaOH. Using 2a as an example, it could be shown that deprotonation followed by addition of an electrophile (Me₃SiCl or Bu₃SnCl) leads to substitution in position 2. Further functionalization was possible by palladium-catalyzed coupling reactions starting from the stannane 4. The diethoxymethyl protected η⁶-tricarbonylchromium complex 5 facilitated acylation in position 2 after deprotonation.