A Pd(II)/Cu(II)-catalyzed chemoselective tandem aerobic
cyclization of phenolic olefins leads to [5,6]-bisbenzannelated spiroketals
or 2-substituted chromans, wherein it was interestingly found that
the presence or absence of base could be responsible for the tunable
selectivity. The [5,6]-bisbenzannelated spiroketals
were achieved from tandem Wacker cyclization-aroxylation
in moderate yields in the absence of base, and 2-substituted chromans
were formed through base-mediated Pd(II)/Cu(II)-catalyzed
tandem Wacker cyclization-Michael addition in good yields.
palladium - chemoselectivity - spiroketals - chromans - Wacker cyclization
