Lithium dechlorination

Sodium bicarbonate is generally added to increase alkalinity and muriatic acid (HCl) or sodium bisulfate (NaHSO ) to reduce it. In general, with acidic sanitizers such as chlorine gas or trichloroisocyanuric acid, ideal total alkalinity should be in the 100—120 ppm range, whereas, with alkaline products such as calcium, lithium, or sodium hypochlorite, a lower ideal total alkalinity of 80—100 ppm is recommended (14). Alkalinity is deterrnined by titration with standard sulfuric acid using a mixed bromcresol green—methyl red indicator after dechlorination of the sample with thiosulfate. Dechlorination with thiosulfate causes higher readings due to formation of hydroxyl ion (32) ... 

The method of Ficini [156], involving treatment of the readily available trichloiovinylamines [157] with three equivalents of alkyllithium, gives access to yneamines with a terminal triple bond. At low temperatures the trichlorovinylamine is dechlorinated with one equivalent of alkyllithium. The subsequent displacement of chlorine by lithium in the intermediary CIOCNR2 takes place when the reaction mixture is heated under reflux. Since part of the... 

Hexakis(2,6-dimethylphenyl)cyclotrisilane, the first known stable three-membered cyclosilane, was prepared in 1982 by Masamune and coworkers from dichlorobis(2,6-dimethylphenyl)silane by the reductive dechlorination with lithium naphthalenide in low yield34. Other cyclotrisilanes bearing substituents of comparable steric bulk have been synthesized analogously. The chemistry of the cyclotrisilanes presently known has recently been reviewed35. 

Preparation of Derivatives. Enoate derivatives are prepared from the corresponding chiral alcohol by treatment with acry-loyl chloride in the presence of Triethylamine and catalytic 4-Dimethylaminopyridine or the appropriate carboxylic acid chloride and Silveril) Cyanide. Alkynyl ethers are readily available from the potassium alkoxide by treating with Trichloroethylene, in situ dechlorination with n-Butyllithium, and electrophilic trapping. Trapping the intermediate anion with a proton source or lodomethane followed by Lindlar reduction of the alkynyl ether affords the corresponding vinyl and l-(Z)-propenyl ether, respectively, while reduction of the alkynyl ether with Lithium Aluminum Hydride affords the l-( )-propenyl ether. 

The product can be reductively dechlorinated with lithium in THF-t-butanol to give a mixture of vinylcyclopropane (32) and ethylidenecyclopropane (33), in 43 and 8 % yield, respectively. Then, by treating the reaction mixture with potassium-t-butoxide in DM SO the vinylcyclopropane (32) can be obtained in 75% overall yield. ... 

Unusual carbanions. Lithium homoenolates are formed from P-aryl-a,P-unsaturated ketones and esters. Their reaction with carbonyl compounds leads to y-lactols and lactones. Reductive dechlorination of a-chloroimines provides a-amino carbanions. Access to 1,2-amino alcohols is assured. 

Lithium-t-Butanol-Tetrahydrohirane. The insecticides aldrin and isodrin became attractive starting materials for the synthesis of compounds of interesting ring systems with the discovery by Bruck, Thompson, and Winstein of a simple method for effecting their dechlorination, that is, replacement of all the chlorine atoms by hydrogen. The polyhalogen compound is treated with lithium ribbon (3 g. atoms per... 

The reaction has been applied also to the adduct (5), readily available by the reactions formulated. This dechlorination with lithium and f-butanol in tetrahydro-furane was attended with some reduction, and the product was a mixture of the... 

Reactions of 1,3-dichloropropanone with Grignard reagents leads to initial reaction at the carbonyl group followed by reductive 1,3-dechlorination on treatment with lithium powder to give cyclopropanols 35 in moderate yield. ... 

Dechlorination of (1) with this combination, equivalent to the original lithium-t-butanol-tetrahydrofurane combination (1, 604-606), led to reduction as well as dechlorination to give (2) and (3).1... 

Catalytic hydrogenation of l-chloropyrrolo[l,2-a]quinoxalines results in removal of the halogen atom. Apparently the dechlorinated products are themselves reducible, and care must be taken in dechlorinations to allow the absorption of only one mole of hydrogen. A recent paper describes reduction of the 4,5 bond in pyrrolo[l,2-a]quinoxalines. 1,5-Dihydro-1-0X0 compounds are resistant to hydrogenation at atmospheric pressure. Reduction of the 1-oxo compound 117 over palladium on charcoal at 2000 psi gave an unidentified tetrahydro derivative. " The dioxo compounds 118 have been reduced with lithium aluminum hydride to give the hexahydro products 119. Heating 4,5-dihydro-4-thioxo derivatives with Raney nickel results in formation of the aromatic, desulfurized compound. Stannous chloride has been used to reduce... 

Lithium-halogen exchange. The reagent is useful for preparation of organo-lithiums from acetal-containing substrates, dihaloarenes (monofunctionalization), and halopyridines. Dechlorination of /V-(/3-chloroalkyl)amides apparently cannot be achieved with BuLi alone (stops at (V-deprotonation ), and the use of LN is required." Of course the N,C-dithio derivatives may be employed in C-C bond formation (remarkably the coupling with aryl and vinyl halides). Barbier-type reactions have been achieved."... 

Ibrning to structurally more complex applications of 100, it has been shown that it can function as a Michael acceptor. For example, when the enolate of 2,4-dimethyl-cyclo-hexen-3-one (152) is treated with 100 in the presence of lithium hexamethyldisilazane (LiHMDS), dichlorovinylation takes place and 153 is formed. On the other hand, with lithium diisopropylamide (LDA) as base, the 1-chloroacetylene derivative 151 is produced [98-100] (Scheme 2-15). The reaction, which also takes place with other 1-chloroacetylenes, most likely involves the Michael intermediate 154 which — depending on reaction conditions — is either protonated or loses a chloride ion. On treatment with copper powder in tetrahydro-furan/acetic acid, 151 is dechlorinated the resulting terminal acetylene has been used for further transformations. 

Dechlorination of 3,4-dichloro-l,2,3,4-tetramethylcyclobutene with lithium amalgam led to the formation of a tricyclic dimer of tetra-methylcyclobutadiene [5], reasonably implicating the cyclobutadiene as an unobserved intermediate ... 

Lithium or sodium dissolving in tetrahydrofuran-t-butanol can accomplish efficient reductive dechlorination of chlorine compounds. This synthetic method has been important in obtaining hydrocarbons via halogenated intermediates. Important examples are conversion of dichlorocyclopropanes (prepared by dichlorocarbene... 

HERCLOR H elastomer was readily dechlorinated by treatment with excess lithium aluminum hydride [LAH] (2.5 moles/mole of Cl) in tetrahydrofuran at SO C. Unreacted hydride was quenched with water, and the polymer samples were isolated for chlorine analyses. The observed pseudo-first-order rate constant for the disappearance of chlorine was found to be 1.9 x 10" minT under these conditions (Fig. 1). 

Figure 1. Linear (A) and semi-log (B) plots showing dechlorination of IIERCLOR H elastomer with lithium aluminum hydride (2.5 moles/ mole Cl) in tetrahydrofuran at SO°C...

A procedure has been described for the determination of irregular head-to-head and tail-to-tail linkages in polyepichlorohydrin. This procedure involves dechlorination of the polymer with lithium aluminum hydride, cleavage of the resultant poly-(propylene oxide) with n-butyllithium, and analysis by gas chromatography to determine the relative amounts of the respective dipropylene glycols. 

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