Lithium ethylamine/dimethylamin

Lithium dissolved in amines of low molecular weight constitutes a useful and convenient reagent for reducing aromatic hydrocarbons to monoolefins.6 Although mixtures of isomeric olefins are usually obtained with primary amine solvents, the use of secondary amines as cosolvents dramatically increases the selectivity of these reductions so that the more thermodynamically stable olefin usually becomes the predominant product. Thus, in the reduction of naphthalene, the amount of A9,10-octalin increases from 52% when pure ethylamine is the solvent to 80-82% when the solvent is an ethylamine-dimethylamine mixture. As another example, the reduction of f-butylbenzene with lithium in pure ethylenediamine produces a product containing 70% of 1-f-butylcyclohexene.7 When a mixture of ethylenediamine and morpholine is used as the reaction solvent, the product contains 84% of 1-f-butyleyclohexene.8... 

I. Ethylamine, anhydrous EK Dimethylamine, anhydrous EK Lithium wire MCB... 

Dihydrobenzopyran (chromane) and its methyl homologs were reduced by lithium in ethylamine and dimethylamine to 3,4,5,6,7,8-hexahydrobenzo-pyrans in 84.5% yields [424. ... 

Kirmse and coworkers have studied the reaction of alkanediazonium ions with amines and with lithium azide Cyclopropanediazonium ions give azo coupling products 6 and 7 with dimethylamine and with ethylamine, respectively (1) K However, no azo coupling of 1 with phenols was observed. In the reaction... 

Solutions of Group I metals in the lower molecular weight amines are more potent reductants than those in liquid ammonia, and as a general rule substrates are more extensively reduced than by the Birch method. o Naphthalene (49 Scheme 48), for example, is reduced by a solution of lithium in ethylamine to a 1 1 mixture of A W- and A -octalins (214) and (215). If ethylenediamine is employed as the medium, the completely saturated decahydronaphthalene is formed, while the proportion of (215) may be increased to 80% by utilizing a (1 1) mixture of ethylamine with dimethylamine. The formation of the more-substituted alkene appears to be a general result for such primary and secondary amine mixtures and has been used to good effect in the reduction of both toluene and cumene to their 3,4,5,6-tetrahydro derivatives (216) and (217), respectively, in ca. 80% yields. A comprehensive review of these kinds of reducing systems, which also draws comparisons with the Birch method, is available,but more recent-... 

Use of a co-amine is embodied in an improved procedure for the preparation of A -octalin. A mixture of 0.2 mole of naphthalene and 250 ml. each of ethylamine and dimethylamine is placed in a flask fitted with a dry ice condenser, 1.65 g.-atoms of lithium wire cut in half-centimeter pieces is added all at once, and the mixture is stirred magnetically for 14 hrs. The solvent mixture is allowed to evaporate and the grayish white residue (containing excess lithium) is decomposed by cautious addition of about 100 ml. of water with cooling. The precipitated product is collected and the filtrate extracted with ether distillation affords 19-20 g. of hydrocarbon found by VPC analysis to contEiin 80% of A "-octalin and 20% of A -octalin. Isolation of the major product in pure form is accomplished by reaction of the mixture with bis-3-methyl-2-butylborane, which adds selectively to the less hindered A -isomer. Oxidation of the product with hydrogen peroxide to convert the adduct into an easily separated alcohol, followed by distillation, affords A" " -octalin of 99% purity in yield from naphthalene of 50-54%,... 

Reduction of naphthalene (2, 241-242, ref. 6a). The reduction of naphthalene with lithium and a mixture of ethylamine and dimethylamine has now been published.1... 

---