Tandem Ugi MCR/Mitsunobu Cyclization as a Short, Protecting-Group-Free Route to Benzoxazinones with Four Diversity Points

A tandem Ugi/Mitsunobu protocol, starting from o-aminophenols, alpha-hydroxy acids, amines and aldehydes gives benzo[b][1,4]oxazin-3-ones of general formula 1 in two high-yielding steps, with the introduction of up to four diversity inputs. The mildness of the methodology allows the stereospecific synthesis of enantiomerically pure products as well as the introduction of additional functional groups. The overall procedure can also be carried out in a one-pot manner.