A facile protocol for the tunable synthesis of 10-hydroxy-1-azaspiro[4.5]deca-3,6,8-trien-2-ones
and benzo[b]pyrrolo[2,1-c][1,4]oxazin-3-ones
is described. A tunable synthesis has been realized by the use of
ZnBr2/oxone and tetra-n-butylammonium
bromide (TBAB)/oxone. The reaction proceeds smoothly with high efficiency
and a broad substrate scope. Mechanistic studies indicate that an N-protecting group-assisted ortho-trapping reaction is involved.
In the transformation, the reaction undergoes α-addition, ipso-cyclization, and ortho-trapping of the resulting spirocyclic
species.