Reaction with lithium iodide

The direct conversion of the acid fluoride into the alkyl iodide by reaction with lithium iodide was also successfully applied to the synthesis of nitrogen-containing pcrfluoroalkyl iodides (Table 3). -... 

As noted above, the selectivity in the reduction of (47 )-G-/err-butyldiphenylsily)oxy-l-[(45 )-2,2-dimethyl-l,3-dioxolan-4-yl]-4-hydroxy-2-hexanone was rather poor, presumably because the two stereogenic centers somehow work against each other [see the corresponding (4.S )-iso-mer in the table on p 4006], However, a refinement of the method, in which the initial reaction with lithium iodide was performed at room temperature and subsequent addition of lithium tris(mrr-butoxy)aluminum hydride (instead of lithium aluminum hydride) was carried out at 0°C, gave much better selectivity d.r. (synjanti) 95 545. 

The conversion of cyclobutyl selenides (221) into cyclopentanones is now possible by conversion into the epoxide (222) and reaction with lithium iodide. This same sequence has led to a short synthesis of ( )-herbertene. ... 

An inversion of alkene geometry is made possible by the reaction of their derived epoxides with lithium halides and TFAA (eq 4) the products of this reaction are the corresponding halo-hydrin trifluoroacetates, which undergo a syn elimination upon reaction with Lithium Iodide. 

Carboxylic esters where R is methyl or ethyl can be cleaved by heating with lithium iodide in refluxing pyridine or a higher boiling amine. " The reaction is useful where a molecule is sensitive to acid and base (so that 10-10 cannot be used) or where it is desired to cleave selectively only one ester group in a molecule containing two or more. For example, refluxing O-acetyloleanolic acid methyl ester... 

As the phosphonium diylides, lithium phosphonium yldiides, first described by Schlosser and Corey (Ph3P=CR-Li R=H, C3H7) [60-62], have a high nucleophilicity and reactivity. Recently, the a-silylated lithium phosphonium yldiide 20 has been prepared from the stable phosphanyl-(silyl)carbene 19 and alkyl-lithium (Scheme 13). The first crystal X-ray diffraction study of such a reagent was proposed for 20 and its reaction with methyl iodide or phosphorus elec-... 

There are also useful procedures for preparation of azides directly from alcohols. Reaction of alcohols with 2-fluoro-l-methylpyridinium iodide followed by reaction with lithium azide gives good yields of alkyl azides.75... 

Reaction of S-b-MM with Lithium Iodide. The reaction was carried out under nitrogen in a 250-mL, round-bottom flask equipped with a magnetic stirrer and a reflux condenser. To a solution of S-b-MM-90/10-wt (3.00 g, 3.0 meq MM) in toluene (100 mL) was added Lil (0.45 g, 3.4 mmol), and the mixture was refluxed for 20 hr. The solvent was partially evaporated, and the polymer was then precipitated from methanol. The precipitate was washed with methanol, water, and again with methanol. The dried polymer was reprecipitated, washed, and dried as described above, yielding 2.58 g of product. Analysis by 1H NMR shows only a trace of MM signal at 3.59 ppm IR (film) y 1723 and 1570 cm-1 (shoulder) ICP 0.106, 0.110 wt% Li (0.156 meq Li/g) expect 1.07 meq Li/g. 

E Selective Wittig reagents. The reaction of 1 with lithium in THF provides LiDBP, which on reaction with an alkyl halide (2 equiv.) and NaNH2 in THF gives a salt-free ylide such as 2 or 3, formed by reaction with ethyl iodide or butyl iodide, respectively. These ylides react readily with aldehydes at —78°, but the intermediate oxaphosphetanes are unusually stable and require temperatures of 70-110° for conversion to the phosphine oxide and the alkene, which is obtained in E/Z ratios of 6-124 1. Highest (E)-selectivity is observed with a-branched aldehydes. 

In this synthesis the geometry of the acyclic double bonds is controlled through their formation as part of the thiane ring. Thiacyclohexanone (711) was converted to 4-thia-l-methylcyclohexene by reaction with methylmagnesium iodide and subsequent dehydration. Metallation of (712) with s-butyllithium and alkylation of the anion with the epoxide (713) gave a tertiary alcohol which was dehydrated to yield (714). A second alkylation of (714) with trails-4-chloro-3-methyl-2-butene 1-oxide (715) completed the carbon skeleton of the Cis juvenile hormone. Reduction of (716) with lithium in ethylamine and then desulfurization with Raney nickel led to trienol (717), a product converted previously to (718). 

Fig. 2.2. Cleavage of aromatic methyl ether using Sn2 reactions. In the dipolar aprotic solvent DMF, thiolate and chloride ions are particularly good nucleophiles for want of solvation through hydrogen bonding. In pyri-dinium hydrochloride a similar effect occurs because for each chloride only one N5 —H5 group is available for hydrogen bonding. The same increase in nucleophilicityin a dipolar aprotic solvent is used to cleave /i-ketomethyl esters with lithium iodide in DMF (cf. Figure 13.29).

Aziridine —> P-lactam.1 This transformation can be effected by insertion of CO into the N-C bond of an aziridine. Thus reaction of N-benzyl-2-methylaziridine (1) with lithium iodide in refluxing THF provides a lithium dialkylamide (a) that reacts with Ni(CO)4 to form the p-lactam 2 in 51% yield. Both reactions probably... 

Selenium-stabilized carbanions can be also generated by 1,4-addition of nucleophilic reagents to a-selanyl a,[3-unsaturated carbonyl compounds. The conjugate addition of trialkylsilyllithium compounds to 133, followed by reaction with allyl iodide, afforded the addition products 134 with good m-stereoselectivity (R = Me dr 86 14 R = Ph dr 94 6) (Scheme 34).214 The addition of lithium dialkylcuprates to 2-phenylselanylcycloalk-2-enones has also been used for the synthesis of natural products.215,216... 

The reactions with germyl iodides were carried out at — 78° with dimethyl ether as solvent. To obtain good yields, the dilithium telluride must be free of ammonia and lithium amides2. 

The 13,17-seco-acid lactone (258), obtained from a Baeyer-Villiger oxidation of 5a-androstan-17-one has been reduced to yield 13,17-seco-5a-androstan-13a,17-diol, whose diacetate on pyrolysis furnished the endocyclic seco-olefin (259 R = OAc) as the major reaction product. A minor product is the corresponding A12 13-olefin.115 Hydrolysis of the acetate (259 R = OAc) to its alcohol (259 R = OH) and formation of the tosylate and the iodide (259 R = I), followed by reaction with lithium dimethylcuprate, afforded a route to A1314-13,17-seco-5a-D-homoandrostene (259 R = Me). The [17a,17a,17a-[2H3]androstene (259 R = CD3) was prepared by treating the iodide (259 R = I) with lithium perdeuteriodimethyl-cuprate. 

Carbamoyl silanes 100 could be prepared by reaction of lithium silylamides 97 with CO at room temperature and under pressure (30 atm) followed by reaction with methyl iodide (Scheme 25)101. The intermediate carbamoyllithium 98 suffers a rearrangement of the silyl group to afford a new lithium (silylcarbonyl)amide 99, which is finally methylated. 

An example prepared by tin-lithium transmetallation is compound 637, which reacts with enolizable ketones, after transmetallation with cerium(III) chloride895. This intermediate was transformed into the corresponding vinylzinc reagent and, after palladium(O)-catalyzed cross-coupling reactions with aryl iodides, was used in the synthesis of the antitumor antibiotic rineomycinone B2 methyl ester940,941. The vinyllithium 627 has also been transformed into the corresponding vinyl iodide by stannylation followed by reaction with iodine. The arylation has been performed in this case by a palladium(0)-catalyzed... 

The synthon they used for the reaction with the anion of methyl glycolate to the tetrahydrofuranone derivative 141 was methyl-4-tm.-butoxybut-2-enoate 140. This compound had been prepared out of the corresponding acetylenic ester91 139 by partial hydrogenation. The 0-ketoester 141 was then C-alkylated by treatment of its potassium salt with methyl-7-iodoheptanoate in DMSO and decarboxylated with lithium iodide in DMF to the ketoester 142 which was claimed to have the more stable conformation with tram side chains. 

Two methodologies for the direct C-2 arylation of thiazoles have been reported. The first one is mediated by both palladium and copper <07T1970>. Thus, the C-2 arylation of thiazole and benzothiazole with aryl iodides is carried out using copper iodide (2 equiv.) and a catalytic amount of palladium acetate under base-free conditions. The other method involves copper-catalyzed arylation with aryl iodides in the presence of lithium t-butoxide <07JA12404>. In general, reactions with lithium tert-butoxide provide better yields than those with potassium fert-butoxide. In addition, arylation with phenyl bromide, chloride or tosylate fails to provide any desired arylation products. 

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