Zinc hydrides reactions with

Lewis and his co-workers have reported three interrelated syntheses of acronycine 208 (81T209). In one synthesis, 2,6-dimethoxy-4-hydroxy-2 -nitrobenzophenone 250, obtained as a minor product from Friedel-Crafts acylation of 3,5-dimethoxyphenol with 2-nitrobenzoylchloride, was treated with 3-chloro-3-methylbut-l-yne under basic conditions. The resultant nitro compound 251 was reduced to the amine 252 with zinc. Upon reaction with sodium hydride in DMSO, this amine provided a mixture of de-N-methylisoacronycine 253 and de-N-methylacronycine 210. T>e-N-methylacronycine 210 was converted to acronycine 208 by methylation with methyl iodide (Scheme 42). 

Chemical ingenuity in using the properties of the elements and their compounds has allowed analyses to be carried out by processes analogous to the generation of hydrides. Osmium tetroxide is very volatile and can be formed easily by oxidation of osmium compounds. Some metals form volatile acetylacetonates (acac), such as iron, zinc, cobalt, chromium, and manganese (Figure 15.4). Iodides can be oxidized easily to iodine (another volatile element in itself), and carbonates or bicarbonates can be examined as COj after reaction with acid. 

Zinc hydride can be isolated from the reaction of LiH with ZnBr2 or NaH with Znl2 ... 

A similar sequence starting with the acylation product (76) from metachlorophenylacetonitrile gives the halogenated tricyclic ketone 83. Condensation of that intermediate with ethyl bromoacetate in the presence of zinc (Reformatsky reaction) gives the hydroxyester 84. This product is then in turn dehydrated under acid conditions (85), saponified to the corresponding acid (86), and converted to the dimethyl-amide (87) by way of the acid chloride. The amide function is then reduced to the amine (88) with lithium aluminum hydride catalytic hydrogenation of the exocyclic double bond completes the synthesis of closiramine (89). This compound also exhibits antihistaminic activity. 

The neutralization values were influenced by reduction with strong reducing agents, lithium aluminum hydride, sodium borohydride, and amalgamated zinc plus hydrochloric acid (35, 46). For the most part, the consumption of NajCOj and of NaOEt decreased in equivalent amounts. This is further confirmation of the assumption that lactones of the fluorescein type or of the lactol type are present. The reaction with sodium ethoxide was shown to be no true neutralization, that is, exchange of H+for Na+, at all, but an addition reaction w ith the formation of the sodium salt of a semi-acetal or ketal ... 

Recently, de Koning et a/.157 have found that hydride transfer takes place exclusively to the 4-position of pyridine, using zinc hydride and magnesium hydride. The reaction is fairly slow and eventually is completed to yield the pyridine complex of bis(l,4-dihydro-l-pyridyI)zinc and its magnesium analog, Zn(NR2)2-2py and Mg(NR2)2-2py, where NR2 is the 1,4-dihydropyridyl residue. H- and 13C-NMR spectral data give consistent answers in agreement with the proposed structures 112 and 113. 

Zinc hydride, a moderately stable sohd slowly decomposed by water, may be prepared by the reaction of LiH, NaH, or LiAlH4 on a zinc halide snch as the bromide or iodide. If organometallic derivatives of zinc of the type Li ZnR +2 are treated with LiAlHi, complex hydrides snch as LiZnHs, Li2ZnH4, and LisZnHs may be prepared. 

Ignition or explosive reaction with metals (e.g., aluminum, antimony powder, bismuth powder, brass, calcium powder, copper, germanium, iron, manganese, potassium, tin, vanadium powder). Reaction with some metals requires moist CI2 or heat. Ignites with diethyl zinc (on contact), polyisobutylene (at 130°), metal acetylides, metal carbides, metal hydrides (e.g., potassium hydride, sodium hydride, copper hydride), metal phosphides (e.g., copper(II) phosphide), methane + oxygen, hydrazine, hydroxylamine, calcium nitride, nonmetals (e.g., boron, active carbon, silicon, phosphoms), nonmetal hydrides (e.g., arsine, phosphine, silane), steel (above 200° or as low as 50° when impurities are present), sulfides (e.g., arsenic disulfide, boron trisulfide, mercuric sulfide), trialkyl boranes. 

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