Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: sbd0517 on September 12, 2014, 10:19:56 AM
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Electrophilic substitution of benzofuran and indole occurs selectively at C2 and C3 respectively. My textbook says that results from "different relative contributions from the benzene ring and the heteroatom towards stabilization of the alternative cationic intermediate", as shown in the attachment. But I still don't get it. How would the difference in the two heteroatoms contribute distinct regioselectivities?
I've tried drawing the resonance contributors of the intermediates, but no difference was found in the case of NH and O.
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Electrophilic substitution of benzofuran and indole occurs selectively at C2 and C3 respectively. My textbook says that results from "different relative contributions from the benzene ring and the heteroatom towards stabilization of the alternative cationic intermediate", as shown in the attachment. But I still don't get it. How would the difference in the two heteroatoms contribute distinct regioselectivities?
I've tried drawing the resonance contributors of the intermediates, but no difference was found in the case of NH and O.
Taking Z: to be your heteroatom look at your resonance stabilised cations.
Please upload the resonance stabilised forms that you have drawn and include mechanisms as to how each is formed.
If the carbocation is in the 2-position, how many resonance stabilised forms are there?
Likewise, if the carbocation is in the 3-position how many resonance stabilised forms are there?
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What the name of this book or reference ??!
edit ... i had found it
Tadashi Okuyama , Howard Maskill, Organic Chemistrya : mechanistic approach