Lithium Bromide related reagents

A further patent for the production of codeine, via codeinone, from thebaine has been published. " Codeine has been shown to be oxidized by manganese dioxide to 14-hydroxycodeinone the reaction is presumed to proceed via codeinone since 6-acetylcodeine is not affected by the same reagent. 6-O-Methanesulphonyl-dihydrocodeine has been shown to react with tetra-butylammonium fluoride, lithium chloride, and lithium bromide, with inversion at C-6, to give the related 6-halogeno-dihydrocodides, but when the ester is heated with sodium iodide in dimethylformamide the product is A -deoxycodeine (deoxycodeine-C) (143). Reductive amination of naltrexone with 2,2 -dihy-droxydiethylamine and sodium cyanoborohydride yields the 6-amino-compound (144 R = OH), which can be converted by carbon tetrachloride and tri-... 

Once again, the nickel-catalysed reactions are far more sensitive to the steric encumbrances, than the palladium-catalysed analogues. Aryl triflates and related sulfonates can serve as the electrophilic reactants in the Kharasch reactions in the presence of an equimolar amount of lithium bromide. The latter additive is a reagent for triflate-bromide exchange, which became a very fast reaction under the Kharasch reaction conditions, since the nickel and palladium-catalysed nucleophilic substitutions of aryl halides and sulfonates are well established reactions, see Chapter 3. In this manner, 2-biphenyl triflate (135) was reacted with 4-tolylmagnesium bromide (136) to give 2-(4-tolyl)biphenyl (137) with a 93% yield [40], respectively. Scheme 8. 

While no concerted attempts to prepare selenaarynes have been reported, the chemistry of several potential precursors has been examined. The 2-lithio-3-bromo derivatives 490 and 491 react with electrophiles as expected for aryllithium reagents and show no tendency at —70°C to eliminate lithium bromide to form a 2,3-didehydroselenophene (492). Similar observations have been reported for the benzolog 493 and the possible aryne 2,3-didehydrobenzo[ft]selenophene 494. As in the corresponding sulfur and oxygen heterocycles, this unusual stability of the 2-lithio derivatives is probably related to the ability of the heteroatom to stabilize an adjacent carbanion. ... 

Related Reagents. Diethylaluminum Chloride Dimethyl-aluminum Chloride Lithium Tetrafluoroborate Magnesium Bromide. 

Other useful organometallic reagents for the preparation of tertiary stibines or related heterocyclic compounds are compounds of lithium, aluminum, tin, copper, zirconium, and other metals. " In most cases, these metal compounds are reacted with antimony chlorides or bromides. Good yields of tertiary stibines were, however, also obtained by the interaction (equation 3) of triaUcylaluminium reagents and tris(dimethylamino)stibine. ... 

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