Sodium hydride, dehydrohalogenation

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 of 3-(bromopropyl)phosphonium bromides by bases constitutes a convenient route to phosphorylated cyclopropanes. 3-(Bromopropyl)triphenylphosphonium bromide, easily obtained by reaction of 1,3-dibromopropane with triphenylphosphane in xylene,was cyclized with a variety of bases, ineluding sodium hydride,sodium hydroxide, sodium ethoxide, or potassium hydride, to give cyclopropyltriphenylphosphonium bromide. Upon treatment of the latter with an extra equivalent of base, the triphenylcyclopropylidene-/l -phosphane is formed (see Section 5.2.3.7.). 

It was found that the use of a triflate salt of PS-PAPT (0.1 equiv.) in conjunction with sodium hydride (2.5 equiv.) could be a remarkably effective method for achieving dehydrohalogenation of RX or debromination of vicinal dibromides to the corresponding olefins [84] (Scheme 6.23). In this case, deprotonation of a triflate salt of PS-PAPT with sodium hydride may have generated the actual strong base species, since sodium hydride itself did not work well or at all under the same reaction conditions. 

Dehydrohalogenation with sodium hydride is a means of making methylenecyclopropanes (eq 23). ... 

Sodium hydride can be used as a dehydrohalogenating agent in dipolar aprotic solvents, such as DMSO or HMPA. Halostilbenes have been converted to the corresponding diarylalkynes in this way. ... 

The resurgent interest in the synthetic utility of 1-nitro-alkenes is evidenced by the variety of recent reports concerning their preparation. " Thus, the dehydration of 2-nitro-alcohols with sodium hydride or dicyclohexylcarbo-di-imide, the dehydrohalogenation of a-halogeno-oximes, and the nitro-selenylation of alkenes followed by oxidative deselenylation all provide 1-nitro-alkenes in moderate to excellent yield. In particular, these methods are all applicable to the synthesis of conjugated cyclic nitro-alkenes and complement those procedures previously reported for the preparation of both cyclic and acyclic nitro-alkenes (Vol. 3, p. 175 Vol. 4, p. 183 Vol. 5, p. 196 Vol. 6, p. 208). 

These reactions are carried out in presence of strong bases such as such as potassium tert-butoxide, sodium hydride [36]. Dehydrohalogenation has been used to synthesize unsubstituted polyphenylenevinylene (PPV) using dichloroxylene/ sodium hydride and DMF solvent, Fig. 3. 

Substituted dibenz[6,/]oxepin-10(l l//)-ones can be reduced with sodium borohydride or lithium aluminum hydride and treated with thionyl chloride to afford the chloro derivatives which undergo dehydrohalogenation when heated or treated with base to give products... 

Weber and coworkers reported the synthesis of novel substituted borazoles. The reaction of boron trichloride with 1,2-diimines 367 provide a mixture of products. The formation of dimeric borazole 369 was explained based on a nucleophilic attack of the chloroborane 370 on the ate complex 368 followed by dehydrohalogenation. Alternatively, a controlled addition of BCR to the diimine 367 results in a clean formation of the imine-borane complex 373 that upon reduction with sodium amalgam and calcium hydride provided the chloroborazole 375 (Scheme 59) <2006EJI5048>. 

Under phase transfer conditions (boiling benzene, 50% aquous sodium hydroxide solution and tetia-n-butylammonium hydrogenphosphate) benzamides are monoalkylated. In the solid-liquid PTC system potassium hydride, tetrahydrofuran and 18-crown-6, acidic trifluoroacetamides are rapidly deprotonated and alkylated with lower kyl, allyl and benzyl halogenides in high yield. Methylation of trifluoroacetamides is carried out under less basic conditions in KOH/acetone. A similar reaction in KOH/DMSO generally allows the efficient reaction of benzamide and acetanilide with primary alkyl halides with secondary halides only moderate yields are accomplished, whereas tertiary halogenides are not alkylated due to dehydrohalogenation. ... 

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