Synthesis and reaction mechanism of a photoremovable protecting group based on 1,4-naphthoquinone

Abstract

5-(Ethylen-2-yl)-1,4-naphthoquinone (1) is a photoremovable protecting group that absorbs up to 405 nm and provides fast and efficient release of bromide or diethyl phosphate. A convenient synthetic protocol to three derivatives of 1 is described and their photochemistry in aqueous and acetonitrile solutions is investigated. The photoenol intermediates that expel the protected substrates were detected by laser flash photolysis and step-scan FTIR spectroscopy. The nucleofugacity of the leaving group and pH are the major factors that determine the reaction pathway.