I was reading some enolate chemistry from Carruthers textbook and came across the selective alkylation of unsymmetrical ketones. The reaction involves blocking one alpha-position of the ketone using an enol thioether, as shown below.
I cannot understand the mechanism of the final step and while searching, I ended up with this from Sciencedirect (Ref.1)
Removal of the thioenol ether protecting group gives the aldehyde function, and under the acidic conditions the β-hydroxy group eliminates to give the mainly (E)-unsaturated enal. This reaction also works if the ketone is reduced to a secondary alcohol with LiAlH4 (69% yield).
My questions are:
- Are enol thioethers the same as thioenol ethers? If not, please draw an example.
- If they are the same, does the deprotection take place through an aldehyde intermediate as stated above?
- Also, please explain the mechanism of this deprotection.
Ref. 1: Warren J. Ebenezer, Paul Wight, in Comprehensive Organic Functional Group Transformations, 1995
Ref. 2: Modern Methods of Organic Synthesis 4th edition, page no. 10