Chapter 16-3_updated

Chapter 16-3_updated - 11 Michaelis–Arbuzov reaction...

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Unformatted text preview: 11 Michaelis–Arbuzov reaction: making phosphonate 22 Horner-Emmons-Wadsworth E product Z product 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 . 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 55 CHEM 262 Wei You Chapter 16. Aldehydes and Ketones (3) 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 + 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. 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...
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This note was uploaded on 06/12/2010 for the course CHEM 261 taught by Professor Austell during the Spring '08 term at UNC.

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Chapter 16-3_updated - 11 Michaelis–Arbuzov reaction...

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