Chem majors, I need your help!

John.

John.

Active member
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Normally I disapprove of people asking for homework help on NS, but it's for me, so therefore it's okay. But really, I have looked all through my books and notes and can't find anything. Almost done with one of my last sets of online problems for OChem II, but I cannot figure this one out.

Any help is greatly appreciated. Thank you!
 
Shit I don't think the picture worked...Attempt number 2

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If you can't see this but don't know what happens when you combine a benzene attached to a dicarbonylated pyrrolidine is combined with 3-OTouselate-1 butyne (shitty naming, I know) and then N2H4 is added, then move along without comment. But if you can't see the pic and do know the result of this situation please contact me, I would be most grateful.
 
I can't see the pic, but OTos is a big red flag...LEAVING GROUP. So I'd guess in the mechanism, it'd be SN2-like...maybe not actually SN2, but the OTos would leave, leaving a butyne anion, which i would assume attacks the pyrrolidine at the carbonyls. classic Nucleophilic Acyl Substitution.
 
though I'm confused about the hydrazine...perhaps they are wanting a wolff-kishner type thing and my previous explanation is incomplete?
 
Sweet, glad someone knows who they're talking about. I got the first step with the Otosylate leaving after Sn2 with the N on the ring being the nucleophile. The online thing I am doing gives feedback, and it says "the role of the hydrazine is to participate in a transamidation reaction, replacing the N-carbonyl bonds in the product of step 1 with new N-carbonyl bonds." We definitely haven't learned about transamidation unless it's just the name for an easy reaction I had never named. I would think the hydrazine would just do the Wolff-Kischner and reduce the C=O bonds to -CH2- but I wouldn't think that would be called transamidation.
 
Ok...What you have done so far makes sense to me. I've never done anything with "transamidation" either.

Anyways, the only two options I see are changing the carbonyl C=O to -CH2-, OR just changing it to a hydrazone ( C=N-NH2 ). I don't see what else could happen. I would think it forms a hydrazone, since the reaction conditions don't include an H+ or H2O workup. Perhaps the question is just worded poorly.
 
Sweet, thanks. Usually I can do these no problem but this set is tough. The last question has a four membered ring with a nitrogen as one member and a methyl substituent on the 1 position. EtOH is added along with catalytic H+. I tried having the N act as nucleophile and end up with the ethyl attached to it, but the program said that was wrong. I can't really think of anything else.I know 4 membered rings are pretty unstable, so would the O from the alcohol act as a nucleophile and somehow open the ring?
 
The nitrogen is connected to a C on either side, bonded to one 1, and has 1 lone pair, right? So it's not really susceptible to nucleophilic attack it seems, since it's plenty electron-sufficient.

I think the H+ will protonate the N, producing a 4 coordinate N (with a formal + charge) transitionally. The electrons in the N-C bond will be pushed to N, and the OH- simultaneously will attack the C.

Is the methyl on a carbon next to the N or across the ring? if it's across the ring it doesn't matter, but if it's next to the ring, you have to decide which N-C bond will be broken, in which case I'd say the one to the carbon with the Methyl attached, since the methyl would stabilize the formal negative transition state through hyperconjugation...

Long story short, I think the product is:

NH2-CH2-CH2-CHMeOH if the Me is on the carbon next to N

or

NH2-CH2-CHMe-CH2OH if the Me is on the carbon across from N
 
You nailed it, the oxygen attacked the carbon with the methyl substituent and opened the ring.I ended up missing both the problems cause I didn't do it in enough tries,but it's not a big deal. The other problem was really weird, after the Ots left and the N had three alkyl substituents, there was a Gabriel synthesis. I thought that needed acidic solution, but apparently hydrazine can be used too to break the rings and make the protonated amine with the alkyl substituents?...Weird, I'm gonna talk to my professor tommorow and try to figure it out.
 
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