5a
Scheme 8 Removal of directing group
Conclusions
In summary, we have reported condition controlled Co(II)-catalyzed
selective [4 + 1] and [4 + 1 + 1] spirocyclization reactions of
aromatic amides with 2-diazo-1H -indene-1,3(2H )-dione
leading to the construction of spiro indene-2,1’-isoindolinones and
spiro isochroman-3,1’-isoindolinones. This current protocol features
with earth-abundant and cheap metal catalyst, avoidance of external
additives, low-cost, clean and abundant oxygen source, and valuable
products with moderate to excellent yields. Moreover, gram-scale
synthesis and the removal of the directing group further demonstrate the
practicability of this protocol to potential industrial applications.
Experimental