[mangolite2]

Hi everyone!Merry Christmas! wee...

hmm, can someone help me check my understanding on this reaction? Firstly, this is a Michael Addition reaction between the Michaael Donor, TBS protected hydroxyacetone and the Michael Acceptor, transbetanitrostyrene. It is postulated that this reaction goes through a reactive enamine transition state between the donor and the organocatalyst which then proceed to a nucleophilic attack to the michael acceptor. Can you check my explanation for this:

In this michael addition reaction, the alpha proton that is abstracted from the Michael Donor is the hydrogen on the carbon with the OTBS group because it is more acidic since it is on the carbon attaached to an electron withdrawing O atom. Hence it is easily deprotonated by a base.

Hence, it forms an transition state as shown. The enamine formed which is a soft nucleophile will then attack the Michael acceptor and add to the carbon with the Ph group "regioselectively" (correct? not regiospecific right?) since this carbon is more electron deficient (the other carbon has a partial negative charge since it is attached to NO2 group where N is partially positive)....The final product is that shown.

Does the explanation sound right? And would there be any other side product formed from this reaction? Like would the enamine attack on the carbon of the ketone? Is it possible for the Michael Acceptor to undergo polymerization? Someone help pls! I totally can't get help from my lab.. and i'm in this on my own independently... Super stressed!!

[movies]

Both aldol (enamine + ketone) and polymerization of the nitro-olefin are potential side reactions.  I think in this case the addition is regiospecific, however, since the attack at the other end of the olefin would leave you with a relatively unstabilized carbanion.

[mangolite2]

thanx for the reply!! =)))))

so its a regiospecific addition reaction? the Nucleophile will attack the beta carbon to form a more stable carbonanion?

uhuh, i've been trying to do this reaction but i do not seem to get my product at all! =(

On my TLC plate, my starting material is still more than 90% present even after 5 days of reaction. Also, i  have a little UV active band at the baseline which i suspect is the polymerised nitro-styrene (is that possible? it should be at the baseline right?)  I have tried different organic solvents such as DMSO, DMF, CH2Cl2, THF and even water to carry out this reaction. So far all failed to give any conversion except DMSO. It is the onlie solvent which gave a possible product spot on the TLC besides the junk at the baseline and my starting material which is higher up on the TLC plate. but the conversion is so little that after purification and it is too little to be observed on NMR! =( In fact, the NMR  has no phenyl protons, and i'm totally confused! Is this reaction not possible at all?

sigh....

[movies]

I'm pretty sure it's regiospecific because it can only reasonably happen one way.  I get -specific and -selective confused sometimes though.

This reaction should be totally possible.  Unfortunately, every time that I have tried to carry out an addition to a nitroolefin I have had the same reactivity problems that you described.  I never figured out why or how to fix the problem.  Sorry!

[HP]

After protection OH with TBS can you make CH2 group to CH:-Na+ and after that do the rection with nitrostyrene in 1:1 stech?