Chapter 15 Reagents with Carbon-Metal Bonds Organometalic Synthesis of Alcohols

Section and Problem Assignments SKIP: Section 15.6 and 15.9 In-Text Problems: 15.2 - 15.7 15.10 - 15.13 End of Chapter Problems: 1 - 3

Sect. 15.1: structure and properties of organometallic compounds Organometallic compounds are prepared by the reaction of halides with metals such as sodium, lithium and magnesium. These reactions involve reduction!!

Organolithium compounds

Formation of Organolithium Reagents Examples ether +2 + butyllithium + + phenyllithium

Organomagnesium compounds: Grignard Reagents

Victor Grignard Nobel Prize 1912 Source: Michigan State University, Department of Chemistry http://www.chemistry.msu.edu/Portraits/PortraitsHH_collection.shtml

SOLVENTS THAT ARE FREQUENTLY USED .. diethyl ether .. Ethers work especially well since they can make complexes with Grignard reagents and solvate them. THF tetrahydrofuran .. .. pentane .. benzene .. .. .. .. .. 1,4-dioxane .. ..

Properties of organometallic compounds polar covalent bond partial negative charge on carbon carbon is basic! don’t memorize Table 15-1!

- BASES AND NUCLEOPHILES + All of these reagents react as nucleophiles or bases: - + Which are bonded, to various degrees, to the accompanying metal.

Sect. 15.2: Reaction of Organometallic compounds with water and acid Organolithium and organomagnesium compounds give alkanes when reacted with water and acid

CH3:- + H+ REACTIONS OF ORGANOLITHIUM COMPOUNDS - - + : d- d+ strong base good nucleophile 57% covalent 43% ionic - + ether + or strong bases react with acids (even water and alcohols) CH3:- + H+ strong base acid

- - - Any -O-H, -S-H, or -N-H bonds are sufficiently acidic to react. + - - .. + .. - + The reaction with H2O also means that you must rigorously exclude water ( and water vapor = air ) from your reactions.

REMOVING A HALOGEN The reaction with water is a way of reducing an alkyl halide ( converting C-X to C-H ). ether Li H2O

MAKING DEUTERIUM COMPOUNDS ether + - .. + Li+ Li+ ether Li D2O phenyllithium This reaction of an alkyllithium compound with water is generally not useful unless you use D2O, which is a way of placing a deuterium atom in your compound.

Sect. 15.3: Reaction of Organometallic Reagents with epoxides Grignard reagent a terminal alcohol

Organolithium d- d+ d+ d- Notice which carbon got the nucleophile.

Sect. 15.4: Synthesis of Alcohols using Grignard reagents ketone tertiary alcohol

THE CARBONYL GROUP .. : - + _ electrophiles attack here nucleophilic at oxygen H+ or E+ .. : d+ d- - + _ electrophilic at carbon Nu: nucleophiles attack here

.. : .. - : : MgBr+ BrMg REACTIONS WITH THE CARBONYL (C=O) GROUP - d- Since oxygen is more electronegative than carbon, the carbonyl group is electron-deficient at carbon, that is an electrophile. : d+ .. - : : MgBr+ - + BrMg new C-C bond The organometallic compound (R-MgBr) behaves as a nucleophile with an unshared pair on the carbon. NUCLEOPHILIC ADDITION TO CARBONYL

SYNTHESIS OF ALCOHOLS Reaction of RMgBr with aldehydes and ketones yields alcohols RMgX + formaldehyde primary alcohol RMgX + other aldehydes secondary alcohol RMgX + ketones tertiary alcohol The type of alcohol depends on whether you use formaledhyde, another aldehyde, or a ketone.

SYNTHESIS PROBLEM from

Sect. 15.5: Synthesis of Alkanes; the Wurtz reaction 2 R-X + 2 Na R-R + 2 NaX

Skip Section 15.6

Sect. 15.7: Preparation of lithium dialkyl cuprates

ALKYLATION WITH R2CuLi R-X + R2CuLi R-R + R-Cu + LiX 0o C R-X + R2CuLi R-R + R-Cu + LiX ether X = Cl, Br, I EXAMPLES (CH3)2CuLi + CH3(CH2)4-I CH3-(CH2)4-CH3 + Corey-House Reaction

MORE LITHIUM DIALKYLCUPRATE COUPLING (CH3CH2)2CuLi + CHBr3

Reaction of cuprates with acid chlorides Cuprates react with acid chlorides to give ketones

Sect. 15.8: Formation of organometallic reagents from alkynes These reagents add to carbonyl groups!! Good stuff!!

Sect. 15.9: Organoboron Compounds revisited Been there, done that!! See Chapter 14.