Chapter 16-3_updated

Chapter 16-3_updated - ichaelisArbuzov reaction making...

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11 Michaelis–Arbuzov reaction: making phosphonate
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22 Horner-Emmons-Wadsworth E product Z product
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33 Horner-Emmons-Wadsworth modification = Wittig Reaction with Phosphonoester ( MeO) 3 P CH 2 -C-OEt O Br CH 3 -O-P-CH 2 -C-OEt O OMe OMe Br ( MeO) 2 P-CH 2 -C-OEt O O MeBr + + S N 2 S N 2 An  α -phosphonoester ( MeO) 2 P-CH 2 -C-OEt O O O H OEt O MeO-P-O - O OMe 1. strong     base 2. Only the  E  isomer is formed + Dimethylphosphate anion *Advantage of using phosphonoesters is that they almost always yield exclusively E product .
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44 Route 2. OCH 3 CHO Br OH CHO Br OMOM CHO Br O Cl NaH, DMF, r.t. 70% BBr 3 CH 2 Cl 2 , -78 o C to r.t. 77% Br CN P CN O OEt OEt P(OEt) 3 150 o C 95% CN OMOM Br THF, r.t. 85% 14 15 16 13 tBuO - K + OH Br O Br O O Br O O Cl NaH, DMF, r.t. 53% NBS, BPO CCl 4 , reflux 88% O Br O Br P O OEt OEt P(OEt) 3 140 o C 77% O Br O P O OEt OEt CN CHO + NaH DME, r.t. NO RXN! LDA THF, 0 o C to r.t. CN OMOM Br 30% Route 1. 10 11 12 13 12 CN OMOM Br
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55 CHEM 262 Wei You Chapter 16. Aldehydes and Ketones (3)
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66 Addition of Nitrogen Nucleophiles Ammonia, 1° aliphatic amines, and 1° aromatic amines react with the C=O group of aldehydes and ketones to give imines ( Schiff bases ) CH 3 CH H 2 N H + CH 3 CH=N H 2 O + + Acetaldehyde Aniline     An imine (a Schiff base) O An imine (a Schiff base) Ammonia Cyclohexanone + + NH 3 H 2 O O NH H +
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77 Addition of Nitrogen Nucleophiles Formation of an imine occurs in two steps Step 1: carbonyl addition followed by proton transfer Step 2: loss of H2O and proton transfer to solvent C O H 2 N-R H H C O: - N-R O H N-R H C + + O H H H H C O H N-R N-R H C O H H O H H C N-R O H H H   An imine + + + + + + H 2 O Note – imines are the prod of rxn of primary amines and C=O; enamines are prepared from rxn of secondary amines and C=O which we will see in Ch 19.
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88 Addition of Nitrogen Nucleophiles Secondary amines react with the C=O group of aldehydes and ketones to form enamines the mechanism of enamine formation involves formation of a tetrahedral carbonyl addition compound followed by its acid- catalyzed dehydration we discuss the chemistry of enamines in more detail in Chapter 19 O H-N H + N H 2 O An enamine Piperidine (a secondary amine) + + Cyclohexanone
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