What is the major product formed in the following reaction?
NBS should do allylic bromination but where will it attack in the larger ring or smaller one ?
Potassium carbonate is not going to give you hydrolysis of a tertiary bromide. It will however close the halohydrin to form an epoxide (1). This intermediate undergoes Lewis acid catalyzed rearrangement to form the spiro compound that is choice (D).
Note that 1 or the carbocation could undergo certain elimination reactions to form (B) and (C). These are probably minor products.