1-Aminobenzotriazole functionalisation using directed metallation: new routes to chromanes and chromenes using intramolecular benzyne trapping by alcohols

Abstract

Metallation of 1-(tert-butoxycarbonylamino)benzotriazole 8 leads to the dianionic species 9 which undergoes smooth reactions with a range of electrophiles, under appropriate conditions. The derived iodide 30 undergoes efficient Sonogashira coupling with a range of alk-1-yn-3-ols to provide the expected arylalkynes 33, total or partial reduction of which leads to the arylpropanols 34 and the (Z)-allylic alcohols 40 respectively. N-Deprotection and exposure to N-iodosuccinimide then led to smooth benzyne generation and intramolecular trapping by the hydroxy functions with iodine incorporation to give the iodochromanes 35 and iodochromenes 41 respectively, in respectable overall yields.