Lecture 8 - 1 CH 310 N T Th 2-3:30 LECTURE 8 Textbook...

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Unformatted text preview: 1 CH 310 N T Th 2-3:30 LECTURE 8 Textbook Assignment: Chapter 16 (begin) Homework (for credit): POW 4 posted- Todays Topics: Organometallic Reagents; Notice & Announcements: Exam 1(conflict): Tuesday, 9/23 7-9 PM WEL 2.122 Check in with Dr Colapret (Exam 1 is in Blackout till Thursday) Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 2 Organometallic reagents have 2 general types of reactions: 1. As Strong bases (Bronsted-Lowry) 2. As nucleophilic reagents: CH 3 CH 2 CH 2 MgBr Regard the alkyl group as R- Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 3 RMgX and RLi RMgX and RLi are valuable in synthesis as nucleophiles the carbon bearing the halogen is transformed from an electrophile to a nucleophile their most valuable use is addition to the electrophilic carbon of C=O groups of aldehydes, ketones, carboxylic esters, and acid chlorides to form a new carbon-carbon bonds Br - C Br CH 3 CH 2 CH 2 H H C - CH 3 CH 2 CH 2 H H Mg 2 + + - carbon is an electrophile carbon is a nucleophile 2 Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 4 A Simple Example: H 3 C CH 3 O CH 3 CH 2 CH 2 H 3 C CH 3 O CH 3 CH 2 CH 2 alkoxide MgBr H OH H 3 C CH 3 O H CH 3 CH 2 CH 2 alcohol MgBr MgBrOH H 2 O Mg(OH) 2 Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 5 Reaction with oxiranes (epoxides) reaction of RMgX or RLi with an oxirane followed by protonation gives a primary alcohol with a carbon chain two carbons longer than the original chain MgBr O O MgBr + OH + A magnesium alkoxide 1-Hexanol Butylmagnesium bromide Ethylene oxide Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 6 Reaction with oxiranes (epoxides) the major product corresponds to S N 2 attack of RMgX or RLi on less hindered carbon of the epoxide MgBr O O- MgBr + H 2 O HCl OH Methyloxirane (Propylene oxide) (racemic) A magnesium alkoxide 1-Phenyl-2-propanol (racemic) + Phenyl- magnesium bromide 3 Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 7 Gilman Reagents Lithium diorganocopper reagents, known more commonly as Gilman reagents Gilman reagents prepared by treating an alkyl, aryl, or alkenyl lithium compound with Cu(I) iodide 2 CH 3 CH 2 CH 2 CH 2 Li + CuI or THF diethyl ether ( CH 3 CH 2 CH 2 CH 2 ) 2 Cu- Li + + LiI Butyllithium Copper(I) iodide Lithium dibutylcopper (a Gilman reagent) Organic Lecture Series Organic Lecture Series Organic Lecture Series Organic Lecture Series 8 Coupling within organohalogen compounds form new carbon-carbon bonds by coupling with alkyl and alkenyl chlorides, bromides, and iodides I 1. Li, pentane 2. CuI CuLi Br 2-Methyl-1-dodecene 1-Iododecane or THF diethyl ether 2 R'Br R 2 CuLiBr R'-R RCu LiBr or THF diethyl ether + + + Organic Lecture Series Organic Lecture Series...
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This note was uploaded on 12/08/2008 for the course BIO 365R taught by Professor Draper during the Fall '08 term at University of Texas at Austin.

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Lecture 8 - 1 CH 310 N T Th 2-3:30 LECTURE 8 Textbook...

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