2- thiophene-, lithium

Organometallic Derivatives of Monocyclic Thiophens - Lithium. Numerous a-substituted thiophens have been prepared via metallation of thiophens with organolithium derivatives. Thus 2-thienyl-lithium has been allowed to react with tetraisopropylthiuram disulphide to give 5-(2-thienyl) A(,A -di-isopropyl-dithiocarbamate in quantitative yield. ° Through the reaction of 2-thienyl-lithium with tellurium in THF, the tellurolate was obtained, which was converted into various products. The reaction of 2-thienyl-lithium with 1,1-dichloro-2,2-difluoroethene has been developed into a very useful method for... 

Carbon-sulfur bonds can be formed by the reaction of elemental sulfur with a lithio derivative, as illustrated by the preparation of thiophene-2-thiol (201) (700S(50)104). If dialkyl or diaryl disulfides are used as reagents to introduce sulfur, then alkyl or aryl sulfides are formed sulfinic acids are available by reaction of lithium derivatives with sulfur dioxide. 

Catalytic reduction of thiophenes over cobalt catalysts leads to thiolane derivatives, or hydrocarbons. " Noncatalytic reductions of thiophenes by sodium or lithium in liquid ammonia leads, via the isomeric dihydrothiophenes, to complete destructions of the ring system, ultimately giving butenethiols and olefins. " Exhaustive chlorination of thiophene in the presence of iodine yields 2,2,3,4,5,5,-hexachloro-3-thiolene, Pyrolysis of thiophene at 850°C gives a... 

A limited number of non-transition-metal derivatives of thiophene will be considered in this subsection. There are no short-range contacts between the lithium atoms originating from the (LiO)6 cores and the sulfur atoms in [Li—O—EMc2 (2-C4H3S)]6 (E = C, Si) (97OM5032), and evidence for Tr-interactions can be found in the X-ray crystal structures of these compounds. Theoretical computations show that a- (S ) Li" " interactions are weak, whereas Tr-Li" contributions are considerable, in accord with the general reasoning on the electronic characteristics of uncomplexed thiophene. 

The bromination behavior of isomeric thienothiophenes (53-55) has been studied in detail. Both the [2,3-b] (53) and the [3,2-h](54) isomers reacted with one equivalent of NBS in acetic acid to give an a-monobrominated product, with some evidence of 2,5-dibromo species also being formed. With 2 mol of NBS these latter products were formed in good yield three molar equivalents led to 2,3,5-tribromothieno-[2,3-h]-and -[3,2-6]-thiophenes (Scheme 28). The monobromo compounds can also be prepared from lithium derivatives quenched with bromine [76AHC( 19) 123]. Apparently the [2,3-c]isomer (55) also reacted initially in the 2-position. 

The addition of some metal ions, such as Mg2+,Zn2+, In3+,orGa3+, and some organic additives, such as 2-thiophene, 2-methylfuran, or benzene, to propylene carbonate-LiC104 improved the coulombic efficiency for lithium cycling [112]. Lithium deposition on a lithium surface covered with a chemically stable, thin and tight layer which was formed by the addition of HF to electrolyte can suppress the lithium dendrite formation in secondary lithium batteries [113]. 

Shatenshtein et al.5 5 5- 591 have also measured rate coefficients for dedeuteration of thiophen derivatives by lithium or potassium l-butoxides in dimethyl sulphoxide or l-butyl alcohol (70 vol. %) in diglyme (Table 178). Interestingly, the 2 position is more reactive than the 3 position and this was reasonably attributed to the —I effect of the hetero sulphur atom. The methyl substituent lowers the reactivity of the 2 position from each position in accord with its +1 effect and consequently the effect was greatest from the 3 position. However, the deactivation from the 5 position was greater than from the 4 position, and this was incorrectly attributed to the +M effect of methyl group operating from the 5 position since... 

To a stirred solution of 45g 3,5-dimethoxybenzoyl chloride and 17.4g thiophen in 300 ml benzene at 0° C, add dropwise 10.5g freshly distilled stannic chloride. Stir one hour at room temperature and add 200 ml 3% aqueous HC1. Separate the benzene layer and wash the aqueous layer with benzene. Dry and evaporate in vacuum the combined benzene layers and distill the red residue (250° C bath/4.5) to get 45g 2-(3,5-dimethoxybenzoyl) thiophen(I). Recrystallize from petroleum ether. Add a solution of 21 g AICI3 in 160 ml ether to a stirred suspension of 6.1 g lithium aluminum hydride in 140 ml ether. After 5 minutes add a solution of 39g(I) in 300 ml ether at a rate giving a gentle reflux. Reflux and stir 1 hour cool in an ice bath and treat dropwise with 50 ml water, then 50 ml 6N aqueous sulfuric acid. Separate the layers, extract the aqueous layer with 3X100 ml ether and dry, evaporate in vacuum the combined ether layers. Can distill the residue (230° C bath/5mm) to get 27g oily 2-(3,5-dimethoxybenzyl) thiophen (II). Recrystallize from petroleum ether. Reflux a solution of 5g (II) in 700 ml ethanol with W-7 Raney Nickel prepared from Ni-Al alloy (see Org. Synthesis Coll. Vol 111,176(1955)) for 6 hours. Filter, evaporate in vacuum and can distill (140/0.01) to get about 2.2g oily olivetol dimethyl ether which can be reduced to olivetol as described elsewhere here. -... 

Thienyl(cyano)copper lithium S Cu(CN)Li xhe reagent is obtained by reaction of thiophene with BuLi in THF at - 78° and then with CuCN at - 40°. The reagent is fairly stable and can be stored in THF at - 20° for about 2 months. It is inert, but is readily converted by addition of RLi or RMgX into a higher-order mixed cuprate, which is as efficient as the freshly prepared cuprate."1... 

Cyclododecene may be prepared from 1,5,9-cyclododecatriene by the catalytic reduction with Raney nickel and hydrogen diluted with nitrogen, with nickel sulfide on alumina, with cobalt, iron, or nickel in the presence of thiophene, with palladium on charcoal, with palladimn chloride in the presence of water, with palladium on barium sulfate, with cobalt acetate in the presence of cobalt carbonyl, and with cobalt carbonyl and tri- -butyl phosphine. It may also be obtained from the triene by reduction with lithium and ethylamine, by disproportionation, - by epoxidation followed by isomerization to a ketone and WoliT-Kishner reduction, and from cyclododecanone by the reaction of its hydrazone with sodium hydride. ... 

Z)-3-(o-Carboxystyryl)thiophene 47b, under acid catalysis, gave only a low yield of tropone 48b (83T819). By means of lithium diisopropylamide (LDA, Parham s reaction), however, cyclization of all three isoelectronic acids 47a-c was achieved. 

During the period covered by this review the preparation of most of the sets of four isomeric monosubstituted dibenzothiophenes have been completed. The successful synthesis of the 1-, 3-, or 4-substituted isomers is due largely to the synthesis of the four monolithiodibenzo-thiophenes by several groups of workers. Despite the success of this work which is due mainly to the established versatility of lithium reagents, the need exists for a separate study of the optimum conditions for the... 

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