[lrw281]

1. Treatment of H with MeLi followed by MeI gives the dimethylated compound K regioselectively. What is the role of MeLi in this reaction?

I have got that MeLi cleaves the silyl enol ether to give a reactive enolate, with negative charge on the oxygen, which can then react with the MeI.

2. In the absence of MeLi, compound H reacts with MeI to give the ring-opened enone L. Propose an arrow pushing mechanism for this transformation.

I'm a bit stuck on this one. not sure how the ring would open to start with, the lone pair on sulphur attacking the methyl group of MeI? Any help would be appreciated.

[orgopete]

So, the first reaction begins with a pair of electrons being donated to the silicon. Do you think the second reaction is different? Hint, what is the missing product?

[lrw281]

The missing product is trimethylsilyl iodide. I'm not sure, would the lone pair be donated to the sulphur instead?

[orgopete]

Obviously, you have the mechanism figured out. If you had a hydronium ion, with a positive charge on the oxygen, could you add electrons to the oxygen?