310-18 - CH 310 N T Th 2-3:30 LECTURE 18 Textbook...

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CH 310 N T Th 2-3:30 LECTURE 18 Textbook Assignment: Chapter 19 Homework (for credit): POW 9 posted Today’s Topics: Enolates & Enamines Notice & Announcements: Organic Lecture Series 2 Enolate Anions Enolate Anions and and Enamines Enamines
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Organic Lecture Series 3 Synthetic Advantages of Synthetic Advantages of Enamines Enamines vs vs Enolates Enolates 1) Avoids proton transfer. 2) Regiochemistry of alkylation can be controlled. (For un-symmetric ketones) 3) Avoids polyalkylation. 4) Avoids O-alkylation. Organic Lecture Series 4 The value of enamines is that the β -carbon is nucleophilic ( same C that was α to carbonyl ) – enamines undergo S N 2 reactions with methyl and 1° haloalkanes, α -haloketones, and α -haloesters – treatment of the enamine with one equivalent of an alkylating agent gives an iminium halide An iminium bromide (racemic) The morpholine enamine of cyclohexanone + Br •• N O S N 2 N O 3-Bromopropene (Allyl bromide) Enamines Enamines -Alkylation Alkylation
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Organic Lecture Series 5 hydrolysis of the iminium halide (salt) gives the alkylated aldehyde or ketone: Morpholinium chloride 2-Allylcyclo- hexanone + HCl/ H 2 O + Br - N O O + Cl - N O HH Enamines Enamines -Alkylation Alkylation Organic Lecture Series 6 enamines undergo acylation when treated with acid chlorides and acid anhydrides N CH 3 CCl O - N O HCl OO N - + Acetyl chloride An iminium chloride (racemic) 2-Acetylcyclo- hexanone (racemic) + + + H 2 O Enamines Enamines -Acylation Acylation
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Organic Lecture Series 7 O CH 3 1 2 3 4 3 1 2 3 4 O 3 1 2 3 4 Addition to Addition to α,β α,β -unsaturated Carbonyls unsaturated Carbonyls When the carbonyl group is conjugated with an alkene, the two groups can act in tandem to expand synthetic utility. α,β -unsaturated carbonyl compounds can exhibit properties of both the carbonyl and alkene group: Organic Lecture Series 8 O 3 1 2 3 4 δ + δ + 1,2 Addition 1,4 Addition Conjugate Addition Michael Addition 3 O 3 :Nu Nu O H 3 H 3 O 3
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Organic Lecture Series 9 • Michael reaction: Michael reaction: the nucleophilic addition of an enolate anion to an α , β -unsaturated carbonyl compound (1,4 addition) – Example: COOEt EtOOC O Et O - Na + EtOH EtOOC O + 3-Buten-2-one (Methyl vinyl ketone) Diethyl propanedioate (Diethyl malonate) Michael Reaction Michael Reaction Organic Lecture Series CH 2 =CHCCH 3 O 2 =CHCOEt O 2 =CHCNH 2 O 3 CCH 2 3 OO 2 =CHNO 2 2 =CHC N 2 =CHCH O 3 2 COEt O Et OCCH 2 O N 3 C=CH 2 3 2 CN O NH 3 , RNH 2 , R 2 These Types of α,β -Unsaturated Compounds are Nucleophile Acceptors in Michael Reactions These Types of Compounds Provide Effective Nucleophiles for Michael Reactions β -Ketoester β -Diketone β -Diester En amin e β -Ketonitrile Aldehyde Ketone Ester Amide Nitrile Nitro compound Amine Michael Acceptors & Michael Acceptors & Nucleophiles Nucleophiles
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Organic Lecture Series 11
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310-18 - CH 310 N T Th 2-3:30 LECTURE 18 Textbook...

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