Chapter 19, Problem 19.60P

Following is a retrosynthetic analysis for an intermediate in the industrial synthesis of vitamin A.

1. (a) Addition of one mole of HCl to isoprene gives 4-chloro-2-methyl-2-butene as the major product. Propose a mechanism for this addition and account for its regioselectivity.
2. (b) Propose a synthesis of the vitamin A precursor from this allylic chloride and ethyl acetoacetate.