3BL-Lecture04 - Welcome to Chemistry 3BL Lecture 4 David...

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Welcome to Chemistry 3BL Lecture 4 David Rabuka
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The Friedel-Crafts Reaction + Cl AlCl 3 (catalytic) + HCl (g) • Consider the Friedel-Craft’s alkylation of 1,1- dimethyl-ethylbenzene by chloroethane. • The major product of the reaction is the para - substituted aromatic, and HCl gas is also released.
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The Friedel-Crafts Reaction Cl AlCl 3 Cl AlCl 3 + • The first step of the mechanism is the formation of an activated electrophile. • A “free” primary carbocation isn’t likely to be formed, but when the electrophile can rearrange to form a secondary or tertiary carbocation, a “free” carbocation may be formed.
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The Friedel-Crafts Reaction Cl AlCl 3 H H H H H H
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The Friedel-Crafts Reaction H Cl AlCl 3 H H H H H + HCl (g) + AlCl 3
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The Friedel-Crafts Reaction + Cl AlCl 3 (catalytic) + HCl (g) Cl AlCl 3 Cl AlCl 3 + Cl AlCl 3 + • In the mechanism for the above reaction, a “free” carbocation is formed. • The remaining two steps in the mechanism are analogous to the last reaction.
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How About “Intra-molecular” Friedel-Craft’s? + Cl AlCl 3 (catalytic) + 2 HCl (g) Cl • When toluene is alkylated by 2,2-dichloro-2,2- dimethylhexane, the aromatic product has the substitution shown above. • The first alkylation is para to the methyl group, and the second alkylation is ortho to the newly formed alkyl substituent.
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How About “Intra-molecular” Friedel-Craft’s? • One can see that the second, intramolecular alkylation is fast, and it isn’t sterically prohibitive to alkylate ortho to the newly formed alkyl substituent. Cl AlCl 3 Cl Cl AlCl 3 HCl (g) + HCl (g) +
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A Retinoid X Receptor to Treat CTCL Cl O MeO 2 C + AlCl 3 (catalytic) O CO 2 Me 1 2 • One can see that a Friedel-Craft’s Acylation takes place ortho to the methyl group of the aromatic substrate (since that’s the least sterically prohibited position).
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A Retinoid X Receptor to Treat CTCL • Compound 3 is known as “Targretin,” developed by Ligand Pharmaceuticals to treat cutaneous T- cell lymphoma (CTCL). O CO 2 Me 1) H 2 C P Ph Ph Ph 2) KOH, MeOH 3) HCl CO 2 H 3 2
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Consider the Possibilities: Cl (2 equiv) AlCl 3 (catalytic) ?
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The Friedel-Crafts Reaction (taken from prelab checklist on page 103): a) Predict the structure of the product from this week’s experiment based on the NMR data provided in your lab manual (pages 107–109). b) Explain why samples of
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This note was uploaded on 01/26/2009 for the course CHEM 3BL taught by Professor Chunmei during the Fall '08 term at University of California, Berkeley.

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3BL-Lecture04 - Welcome to Chemistry 3BL Lecture 4 David...

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