[xanthi]

 hello..i'm a postgraduate student at the universtity of patra on medicine field..and i have a critical (for me) question..could someone please explain to me the mechanism of Knorr's pyrrole synthesis? i also wanna know if there are any restrictions on the substitutes.. answer me a.s.a.p.!!! plz help meeee

[xanthi]

oh! i forgot to mention that i already have read the topic about knorr's pyrrole synthesis and mechanism..i have spent many hours and i wasn't able to find the exact mechanism with all the information i needed, especially about the substitutes of each carbon..so if anyone could help me with their knowledge i would be greatful..

[sjb]

Wikipedia is your friend.

Have you seen http://en.wikipedia.org/w/index.php?title=Knorr_pyrrole_synthesis&oldid=162782944  - if you need a more detailed mechanism, let us know...

S

[xanthi]

Wikipedia is your friend.

Have you seen http://en.wikipedia.org/w/index.php?title=Knorr_pyrrole_synthesis&oldid=162782944  - if you need a more detailed mechanism, let us know...

S

hmmm...that was between the first pages i searched when i started looking about that subject.. unfortunately i need something much more detailed than wikipedia.that's why i registered to this forum..i couldn;t find anything about the carbons' substitutes..if there's any ristriction..you know..could you help me?

[sjb]

I don't think there's that much of a restriction as such, my only comment on the synthesis as presented on wiki is that alpha amino ketones may self condense, so you may need an electron withdrawing group on the right-hand molecule (the beta ketoester) to help form the enamine intermediate faster.

S

[xanthi]

could you take a look at this page?

http://www.unine.ch/chim/ecsoc-2/ECSOC-04.html

there are specific substitutors at each carbon..is there any difference between this reaction and that on wikipedia? which one shows the mechanism of pyrrole synthesis better? please make a comment..

[sjb]

I assume you mean figure 9 on that page?

If so, then there's no real difference between that and the wikipedia page as such, your link perhaps shows a bit more clearly that the amino ketoester could come from the same molecule as the ketoester, and so the substituents at 2 and 4, and at 3 and 5 can be the same, but I don't think that's a rule as such - it may be but it may mean not a Knorr as such, I'm not fully conversant with names and tend to try and remember basics of mechanisms themselves.

The basic picture I would draw if asked to describe a Knorr would look pretty much like figure 9, perhaps without the chirality in the last intermediate or the amine, as I don't think they're relevant to the final compound.

S