[tvtokyo]

I have this problem:
I known that reaction with TsOH would replace -OH groups with TsO (substitution reaction). (Et)3N would therefore act as a base to abstract H to form an alkene. The problem is i know it should be an E1cb reaction but how do I obtain an alkene? I tried to draw the mechanism but comes to no solution can anyone help or am i in the wrong direction? Thank you!

[OrgXemProf]

If you're convinced that the product MUST be a substituted cyclopent-2-en-1-one and that the reaction MUST proceed via an E1cb mechanism, then you might consider the following reaction sequence:

1. Use Et₃N + H₃C-SO₂Cl to convert ROH into the corresponding mesylate ester, ROMs. Now you have a good leaving group.

2. Use Et₃N to abstract the O=C-CHOMs proton to form a resonance-stabilized carbanion.

3. In a subsequent step eliminate ^-OMs to form a carbene, which then is likely to undero 1,2-hydride shift to afford the desired substituted cyclopent-2-en-1-one.

Just wondering: Are you working backwards from the answer, or do you simply consider formation of an alpha,beta-unsaturated ketone to be the most likely outcome given the reaction conditions that you posted?

[tvtokyo]

Just a simple assumption (i.e. not work back form answer)
Thanks for your reply

I have another question
For this reaction would it proceed via Sn2 or elimination
I think SN2 since the solvent is polar aprotic and SH- is not really a strong base???
So I think SH would substituted Br with a inversion in configuration?? Thanks!

[orgopete]

I have my doubts that the enone is the product.