[trinitrotoluene]

For the cyclization shown, is this the correct mixture of isomers?


This is what I can up with.
I guess I should mention that I am specifically asking about the 5-exo-trig cyclization.


Thanks!

[magician4]

the scheme looks ok to me sofar

however, some thoughts that instantly came to my mind:

- iodine under alkaline conditions wouldn't be my first choice if I was in for an iodonium-ion intermediate, as I would expect formation of iodohydrines to become a serious side problem

- asides from the furanes shown, I would expect pyranes to form, esp. as the NHTs - group should provide some sterical shielding (even from the β-position ) with respect to the carbon you'd need to attach your oxygen to, if the the furane was to be formed

- last not least, by the same token, I would expect some selectivity with respect to which one of the two iodonium - isomers (and respective products resulting thereof) should be somewhat overrepresented : the carbon bearing the nitrogen is asymmetric, and "Ts" is quite a whopper

maybe these thoughts might be interesting to you


regards

Ingo

[trinitrotoluene]

the scheme looks ok to me sofar

however, some thoughts that instantly came to my mind:

- iodine under alkaline conditions wouldn't be my first choice if I was in for an iodonium-ion intermediate, as I would expect formation of iodohydrines to become a serious side problem

- asides from the furanes shown, I would expect pyranes to form, esp. as the NHTs - group should provide some sterical shielding (even from the β-position ) with respect to the carbon you'd need to attach your oxygen to, if the the furane was to be formed

- last not least, by the same token, I would expect some selectivity with respect to which one of the two iodonium - isomers (and respective products resulting thereof) should be somewhat overrepresented : the carbon bearing the nitrogen is asymmetric, and "Ts" is quite a whopper

maybe these thoughts might be interesting to you


regards

Ingo

Thanks Ingo definitely some good insight. ^__^

As for the halohydrin, I just assumed there was no water floating around for this problem and the OH would be the other strongest nucleophile to pop open the ring.

Also, I think the pyran doesn't form because 6-endo-tet is not favored according the Baldwin's rules. however I would assume that the iodium has some considerable p-character and is kinda in the middle of sp3/sp2 and 6-endo-trig is favored. I could definately see this as a possibility

I had this question on a problem set and I got it wrong so I'm trying to figure out why.
I "got the wrong diasteromers" the correct answer had the product on the left with an arrow pointing to NHTs as "mixture of isomers here".

I would guess this has something to do with the sterics that you are talking about concerning the NHTs and iododium. But it seems dicey because the reactant is to be presumed a racemic mixture in regards to the NHTs group as no stereochemsitry was given. Unless the stereochemistry of the NHTs bearing carbon would be irrelevant for that argument.

[magician4]

As for the halohydrin, I just assumed there was no water floating around for this problem and the OH would be the other strongest nucleophile to pop open the ring.

you've got a point here: maybe I'd better had thought of some pyridine-iodine complex type of reagent here, just like in Fischer water analysis...
However, I would make RO^- the attacking nucleophile under these conditions

Also, I think the pyran doesn't form because 6-endo-tet is not favored according the Baldwin's rules. however I would assume that the iodium has some considerable p-character and is kinda in the middle of sp3/sp2 and 6-endo-trig is favored. I could definately see this as a possibility

question to me here is, whether the iodonium ion really could be compared to , lets say , a cyclopropane (where I would agree to your analysis) , resp. how much "carbeniumion / iodid " the situation already is.
As Baldwin applies to kinetics, the high reactivity at such an center might spoil selectivity, i presume.
However, maybe I'm just being too anxious...

(...) Unless the stereochemistry of the NHTs bearing carbon would be irrelevant for that argument.

I think it well might be relevant: let's say you're starting with a racemic mixture, and if asymmetric induction was the name of the game here, than the (future) orientation at the furane ring - closing carbon  should lead to a mixture of two different substances  (for example racemic d/d and l/l in mixture with also racemic d/l and l/d) , depending to the orientation "there to be in the future"


regards

Ingo