Reagents, lithium iodide

Enamines are stable to Grignard reagents, methyl iodide and lithium aluminum hydride. 

Oxygen-substituted allylchromium reagents are conveniently generated from vinyloxi-ranes by chromium(II) chloride in the presence of lithium iodide and aldehydes with high anti diastereoselectivity14. qh oh... 

In summary, we have examined several new methods for cleaving ester groups in poly(styrene-b-alkyl methacrylates). Short blocks of methyl methacrylate are very difficult to hydrolyze, but can be cleaved with reagents such as lithium iodide and potassium trimethylsilanolate. These latter reagents, however, result in side-reactions which appear to crosslink the polymer. 

Reduction to Halocarbons. The best conditions for the reductive chlorination of ketones use the reagent combination Me2ClSiH/In(OH)3 (Eq. 241).331 Examples include conversions of aryl ketones to benzyl chlorides, ethynyl ketones to propargyl chlorides, and alkyl ketones to alkyl chlorides (Eq. 242).331 Addition of lithium iodide to the reaction mixture yields the corresponding iodide product. The combination of TMDO/I2 reductively iodinates aryl ketones and aldehydes in good yields (Eq. 243).357... 

The solvents utilized were all analytical grade reagents further purified by distillation. A-(3-Triethoxysilyl)-propanamine (APTES), nonanedioic acid monomethyl ester, 12-nitro-dodecanoic acid, octadecanoic acid, octadecylamine, and lithium iodide were Aldrich samples and were used as received. Silicon wafers were supplied by International Wafer Service, Palo Alto, CA. 

Arnold and co-workers also reported the deprotonation of alkoxy imi-dazolium iodides with -butyl lithium to yield lithium alkoxide carbenes (Scheme 3).14 Single crystals of one of the complexes were grown from a diethyl ether solution, and revealed a dimer of LiL with lithium iodide incorporated to form a tetramer of lithium cations (7). The lithium-NHC bond distance of 2.131(6) A is similar to that of the lithium amide carbene 4. Also as in 4 there is distortion of the lithium-NCN bond which has an angle of 152.3°. The C2 carbon resonates at 200 ppm in the 13C NMR spectrum which is a relatively high-frequency, possibly as a result of the incorporated lithium iodide. The lithium salts were able to act as ligand transfer reagents and react with copper (II) chloride or triflate to afford mono- or bis-substituted copper(II) alkoxy carbene complexes. 

Homoconjngate addition to cyclopropanes. Corey and Fuchs have investigated the reaction of cyclopropanes with organocopper reagents as a possible synthetic route to prostanoids. For example, the tricyclic lactone ester (1) reacts with divinylcopper-lithiura (2.0 eq.) in ether at -12° (19 hr.) to give the vinylcyclopentane lactone ester (2). Tliis product was treated directly with lithium iodide (5 eq.) in pyridine (1,615-616) at reflux for 3 hr. to give the lactone (3) in about 37% yield. 

The reagents lithium dialkylcopper (dialkyl cuprates, also called Gilman reagentsf react with alkyl bromides, chlorides, and iodides in ether or THF to... 

Use.1 The reagent has been used in the same way as dimethylcopperlithium for conjugate addition to a,/3-unsaturated ketones however, with the present reagent various salts (lithium iodide, lithium bromide, etc.) must be present. The tri-/i-butyl phosphite and tri-n-butyl phosphine complexes have been prepared but are less useful. 

This reaction had been effected previously with lithium iodide in refluxing 2,6-lutidine (1, 615-616). This combination afforded 25-28% of starting material, 49-51% of the desired acetoxy acid, and 5-10% of the hydroxy acid. Use of the mercaptide reagent converted the acetoxy ester into 3/3-acetoxy-A5-etiani c acid in 92% yield (25°, 24 hours). 

Several other reagents have been used to affect demethylation, such as lithium iodide 70>, ethanolamine 74>, and morpholine 12>. With these reagents, simple displacement reactions are observed,... 

In dealkylation experiments although removal of methyl groups can be achieved readily by reagents such as lithium iodide in hot collidine (ref. 144) milder conditions are frequently obligatory. 

ALDEHYDES Bis(4-methylpiperazinyl)aluminum hydride. Di(r) -cyclopentadienyl)-(chloro)hydridozitconium(IV). Dihalobis(triphenylphosphine)paIIadium(H). 7,8-Dimethyl-l,5-dihydro-2,4-benzodithiepin. Grignard reagents. Lithium bis(ethylene-dioxyboryOmethide. 3-Methyl-I-phenyl-2-phospholene. 2-Methyl-2-thiazoline. Methylthioacetic acid. 3-Methylthio-l,4-diphenyl-s-triazium iodide. Sodium meth-oxide. Methylthiomethyl N,N-dimethyldithiocarbamate. Sodium tetracarbonylferrate(II). Tetra-n-butylammonium borohydride. Triethylallyloxysilane. N,4,4-Trimethyl-2-oxazolinium iodide. 

An enolate anion is a nucleophile and, unlike Grignard reagents and organolithium reagents, reacts easily with the electrophilic carbon of an alkyl halide. Although both the oxygen and the carbon are nucleophilic (sec. 9.3.B), the carbon is usually the most nucleophilic site in the enolate. As with other carbon nucleophiles, such as acetylides (sec. 8.3), the electron rich carbon attacks the electrophilic carbon of the halide to form a new carbon-carbon bond, with lithium iodide (Lil) as the byproduct. 

---