Technix540 Posted October 31, 2020 Posted October 31, 2020 (edited) Need to know exact mechanism and absolute stereochemistry? This is a beta-gamma unsaturated ketone and we haven't discussed them in class at all. I might be a little tired in the head (exam coming up), but this can't simply be a protonation of the double bond, followed by a nucleophilic attack on the formed carbocation could it? Does anybody have any tips on what type of reaction this is? Edited October 31, 2020 by Technix540
John Cuthber Posted October 31, 2020 Posted October 31, 2020 1 hour ago, Technix540 said: Does anybody have any tips on what type of reaction this is? Imaginary, HSiPr does not exist. 1 hour ago, Technix540 said: but this can't simply be a protonation of the double bond, That's a fair point given... "HSiPr , Base" Protonation seems unlikely What's your view on a deprotonation of something by that base?
Technix540 Posted October 31, 2020 Author Posted October 31, 2020 (edited) 7 hours ago, John Cuthber said: Imaginary, HSiPr does not exist. That's a fair point given... "HSiPr , Base" Protonation seems unlikely What's your view on a deprotonation of something by that base? Hi John, thanks for your reply. I thought HSiPr was a thiol with an isopropyl group (HSR)?. In the presence of base, the most acidic H should get deprotonated (alfa-position either left or right of the carbonyl) Or perhaps the base deprotonates the thiol thus increasing its nucleophilicity. The gamma-position is attacked by the thiol since the delta-position is blocked due to sterics which would arise from the two isopropyl groups. Stereochemistry, since the top face is hindered by the isopropyl group (wedged line) the attack could be made from the bottom face (dashed line)? Edited October 31, 2020 by Technix540
chenbeier Posted October 31, 2020 Posted October 31, 2020 10 hours ago, John Cuthber said: Imaginary, HSiPr does not exist. That's a fair point given... "HSiPr , Base" Protonation seems unlikely What's your view on a deprotonation of something by that base? Its isopropanthiol (CH3)2CHSH The writing HSiPr could be misunderstanded as Si = Silicon, even the compound makes no sense.
John Cuthber Posted November 1, 2020 Posted November 1, 2020 By convention... iPrSH exists. You could use HSiPr The point stands that , in the presence of base, you are not going to protonate anything much. On 10/31/2020 at 9:30 AM, Technix540 said: Or perhaps the base deprotonates the thiol thus increasing its nucleophilicity. That's much more realistic.
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