In the book "Organic Chemistry" by Clayden et al. p 343 it is stated that this substrate reacts very slowly through both the SN1 and SN2 pathways. It is shown side by side with neopentyl chloride as an example of notoriously unreactive compounds.
I get that being tertiary might slow down SN2 to counteract the effect of the adjacent carbonyl. But why would SN1 not still be good?
My question is: why does this substrate react slowly through both SN1 and SN2?