A Brønsted acid catalyzed tandem process to access
densely
functionalized chromeno[3,2-d]isoxazoles with good
to excellent yields and diastereoselectivities was disclosed. The
procedure is proposed to involve a 1,6-conjugate addition/electrophilic
addition/double annulations process of alkynyl o-quinone
methides (o-AQMs) in situ generated from o-hydroxyl propargylic alcohols with nitrones. Mild conditions,
good functional group compatibility, easy scale-up of the reaction,
and further product transformation demonstrated its potential application.