Lecture 2B - Reversible Additions to Carbonyls 3a . Imines...

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Unformatted text preview: Reversible Additions to Carbonyls 3a . Imines (Biological Reactions) 3b . Enamines 4 . Cyanohydrins (Biodefence weapon ) Lecture 2B Top 12 reactions 1. 1,1- halo hydrin formation 2. a) Hydration b) Acetal formation 3. a) Imine formation 8. a) O xidation with Jones Reagent (Aldehydes) b) Bayer-Villiger o xidation (Ketones) b) En amine formation 4. Cya n ohydrin formation 5. Grignard Addition 6. Wittig Reaction 7. Reduction 9. Deuterium exchange 10. - Halogen ation 11. -alkylation 12. Ald ol formation Rxns 1- 7 are Nucleophilic Additions to Carbonyl R -C= O H : nu Halides ( Cl- ) Oxygen (H 2 O , R O H) Nitrogen (1 , 2 , 3 amines ) Carbon (-C N, Grignard, Wittig) Hydrogen (hydride) (NaBH 4 , LiAlH 4 ) 3a,b Nucleophilic attack by nitrogen nucleophiles H C H O N H + O .. H C H N + + H 3 H 2 H . . Simplest case Note: Most simple imines decompose in water to give the parent carbonyl group. Carbonyl group is the thermodynamic resting place Aldimine Imino group Aldehyde Carbonyl group 3a) Imine Formation with Primary Amines (R = alkyl) and ammonia (R = H). H O H N R N H + O + H 2 R H 2 3b) Enamine Formation with Secondary Amines (R = alkyl) H O H N R R N H + O + HR 2 H 2 C O C O NH 2-H .. NH 2 R .. + + multi step multi step ammonia mine Reaction outcomes depends on type of amine used and ability to generate H 2 O. ( Imine ) ine 1 amine ( Imine ) C O NHR 2 .. C N R R H H .. +-H + multi step 2 amine ( Enamine ) C O NR 3 .. + 3 amine Product very unstable An Aside: Comparison of Nomenclature for Alcohols vrs Amines Alcohols H 2 O RCH 2 O H (Primary alcohol) ----- R 2 CH O H (Secondary alcohol)--- Amines N H 3------------------------------ (Primary Amines)------------ R 3 C O H (Tertiary alcohol)--------- R O R (ether) R O + R (oxonium salt) R--------------- ------------- (Secondary Amine)- -------------...
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Lecture 2B - Reversible Additions to Carbonyls 3a . Imines...

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