Dehydrohalogenation lithium carbonate

A modification introduced by Joly allows clean dehydrohalogenation of (5a or 5)8) 2,4-dibromo-3-ketones to -3-ketones. This involves the use of an excess of lithium carbonate in DMF, which presumably prevents the... 

Dehydrohalogenation Benzyltrimethylammonium mcsitoate. r-Butylamine. Calcium carbonate. j Uidine. Diazabicyclo[3.4.0]nonene-5. N.N-Dimethylaniline (see also Ethoxy-acetylene, preparation). N,N-Dimelhylformamide. Dimethyl sulfoxide-Potassium r-but-oxide. Dimethyl sulfoxide-Sodium bicarbonate. 2,4-Dinitrophenylhydrazine. Ethoxy-carbonylhydrazine. Ethyldicyclohexylamine. Ethyidiisopropylamine. Ion-exchange resins. Lithium. Lithium carbonate. Lithium carbonate-Lithium bromide. Lithium chloride. Methanolic KOH (see DimethylTormamide). N-PhenylmorphoKne. Potassium amide. Potassium r-butoxide. Pyridine. Quinoline. Rhodium-Alumina. Silver oxide. Sodium acetate-Acetonitrile (see Tetrachlorocyclopentadienone, preparation). Sodium amide. Sodium 2-butylcyclohexoxide. Sodium ethoxide (see l-Ethoxybutene-l-yne-3, preparation). Sodium hydride. Sodium iodide in 1,2-dimethoxyethane (see Tetrachlorocyclopentadienone, alternative preparation) Tetraethylammonium chloride. Tri-n-butylamine. Triethylamine. Tri-methyiamine (see Boron trichloride). Trimethyl phosphite. 

DEHYDROHALOGENATION Dimethyl sulfoxide. Lithium carbonate. Potassium r-butoxide. 

Chloro ketones have been observed in tin(IV) chloride catalyzed acylations of isopiene as part of high-yielding synthetic approaches to tagetones (12) and ocimenones (13 Scheme 15). Typically, it was not necessary to isolate these, dehydrohalogenation to mixtures of cis- and rran -dienones being accomplished using lithium fluoride and lithium carbonate in DMF. 

Dehydrohalogenation. White and co-workers have reported a very efficient dehydrobromination of (1) to (2) by use of lithium chloride and lithium carbonate in HMPT (105°). The same conditions have been used for conversion of (3) to... 

A cortisone synthesis using remote functionalization at an unactivated carbon centre has been achieved.97 Cortexolone (224) was converted into the 5a-H,3j3-OH derivative (formation of the bismethylenedioxy-compound followed by lithium-ammonia-ethanol reduction). Inversion98 of 3)8- to 3 -OH followed by esterification with m-iodobenzoic acid produced (225), which on irradiation in methylene chloride containing phenyl iodide dichloride gave the 9 a -chloro-derivative (not isolated). This was dehydrohalogenated and saponified by methanolic potash to yield (226) (75%) and thence, by further known steps, cortisone acetate. 

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