Lithium ethylamine

In the following sections, we will review the marine isonitriles by skeletal types. This permits comparison of their differences and may suggest biogenetic clues. Skeletal frameworks are generally revealed by reducing the isonitrile with lithium/ethylamine to the corresponding hydrocarbon. Where trivial names have been assigned for skeletal types and for compounds, we shall use these as reported in the literature. In some cases, when structures related to previously mentioned compounds are discussed, formula numbers will be employed. 

Desulfonylation Lithium-Ammonia, 158 Lithium triethylborohydride, 168 Magnesium-Methanol, 170 Sodium dithionite, 281 Sodium naphthalenide, 294 Desulfurization Lithium aluminum hydride-Bis(cyclopentadienyl)nickel, 158 Lithium l-(dimethylamino)naph-thalenide, 165 Lithium-Ethylamine, 158 Dethioacetalization (see Hydrolysis of thioacetals and -ketals)... 

Lithium butyldimethylzincate, 221 Lithium sec-butyldimethylzincate, 221 Lithium-Ethylamine, 158 Lithium o-lithiophenoxide, 166 Lithium methoxyacetylide, 166 Lithium phenylacetylide, 244 Lithium trialkylzincates, 221 Lithium trimethylsilylacetylide, 206 Lithium trimethyl(tributylstannyl)-aluminate, 320... 

DESULFONYLATION Lithium-Ethylamine. Sodium-Ethanol. Sodium amalgam. Tetrakis(tnphenylphosphine)palladium. DESULFURATION ... 

Lithium-ethylamine reduction at one or both double bonds of carvone, and of carvenone (58) to carvomenthone only, is reported.The effect of solvent on the lithium or potassium amide-reduction of p-cymene to menthenes and menthadienes has been examined.Hydrogenation of carvone (Vol. 4, p. 32), using palladium-polysaccharide exchange resin, favours endocyclic over exocyclic double-bond reduction, more so than with Pd-C or Pd-BaS04, whereas platinum or rhodium on exchange resins exhibit no special selectivity.Optimum conditions for the catalytic hydrogenation of thymol, and the catalytic dehydrogenation of menthol, to menthone have been determined.Cathodic reduction of carvomenthone (to... 

Lithium-Ammonia, 234-236 Lithium-Ethylamine, 236 Lithium aluminum hydride, 236-237 Lithium aluminum hydride-Copper(I) iodide, 237... 

Protection or reductive deoxygenation of alcohols and ketones. Ireland et al.2 have found that N,N,N, N -tetramethylphosphoroiiamidates (TMPDA derivatives) of alcohols and of ketone enolates are reduced in high yield by lithium-ethylamine. They are readily prepared by phosphorylation of alcoholate or enolate anions. The complete sequence is as follows. The alcoholate anion is simply prepared by treatment of an alcohol with a slight molar excess of n-butyllitliium. The enolate anions of saturated ketones are prepared by treatment with lithium diisopropylamide. In the case of a,/J-unsaturated ketones, lithium-ammonia reduction or conjugate organometallic addition is suitable. For phosphorylation of the Jnion a fivefold excess of N,N,N, N -tetramethyldiamidophosphorochloridate in 4 ] dimethoxyethane (or THF)-N,N,-N. N -tetramethylethylenediamine (TMEDA) is used. The reaction is complete after... 

Henbest found lithium-ethylamine an effective reagent for the reduction of allylic esters or ethers to olefins. For example a solution of 0.4 g. of the benzoate of A -cholestene-3/3-ol in 20 ml. of ethylamine on reaction with 0.1 g. of lithium... 

Henbest found that lithium-ethylamine also is an effective reagent for the desul-I lii izution of ethylenethioketals." The Diels-Alder adduct of benzoquinone with 2 moles of butadiene, for which Henbest deduced the configuration (4), was converted... 

A. Alkaloids of Type I, not containing a Functional Group at C-11.— -Acetyl-cycloprotobuxine-D (124), isolated from B. sempervirens, gives on acetylation the already known iViV -diacetylcycloprotobuxine-D (125). Methylation (HCOjH-HCHO) gives JV-acetylcycloprotobuxine-B (126), which is different from the known N-acetylcycloprotobuxine-C (127). Deacetylation with lithium-ethylamine has not been attempted. 

Two almost simultaneous communications reported the successful syntheses of a-cedrene (123) and cedrol (124). Both syntheses were modelled along a proposed biogenetic scheme, and as such the penultimate goal was the generation of the cation (125) which should, and did, undergo a smooth acid-catalysed cyclisa-tion to a-cedrene. The two pathways to this cation differed in several respects yet practically coincided at the key spiro-dienone ester (126, R = Me and R = Et ). Whereas Crandall and Lawton completed the synthesis by formic acid treatment of the alcohol (127), Corey et al. found that similar treatment of the diol (128) also yielded a-cedrene, albeit in lower yield. Alternatively, the ene-diol (129) was converted into a-cedrene in better yield by formic acid treatment, thermolysis of the derived formates and subsequent lithium-ethylamine reduction of the diene (130). Finally, cedrol (124) was obtained by boron trifluoride cyclisation of the enol-acetate (131), followed by methyl-lithium treatment of the intermediate cedrone. 

The acid (337) prepared from (-)-abietic acid was reduced by lithium ethylamine-terf-amyl alcohol to compound 338. The methyl ester of 338 was hydroxylated and the resulting diol cleaved to give diketone 339. The latter was cyclized by treatment with acid to the a,/8-unsaturated ketone (340). Although rings A and can be easily substituted by appropriate reactions to derive the corresponding aconitine-type alkaloid, the major problem with this route is the introduction of the ring C substituents. 

Lithio-1 -trimethylsilylpropyne, 638 Lithium, 274, 351 Lithium-Alkylamines, 322 Lithium-Ammonia, 322-323,463, 502 Lithium-Ethylamine, 12 Lithium-Hexamethylphosphoric triamide, 323... 

The reductive removal of either an alcoholic or ketonic function can be effected by treatment of the alcoholate or enolate anion with tetramethyldiamido-phosphochloridate [(MejNljPOCl] to form the ester, followed by reduction with lithium-ethylamine [e.g. (129)—+ (131)]. Diethylphosphochloridate can be used similarly. The reactions are applicable to primary, secondary, or tertiary alcohols the intermediate esters are stable to a variety of common reagents. 

Lithium(3,3-dimethyl-l-butynyl)-l,l-di-ethoxy-2-piopenyl cuprate, 300 Lithium dimethyl cuprate, 301-302 Lithium di-n-octylcuprate, 356 Lithium diphenylphosphide, 302 Lithium (fl-(E)-propenyl cuprate, 302-303 Lithium divinyl cuprate, 190 Lithium-Ethylamine, 284-286, 472 Lithium fluoride, 244 Lithium hexamethyidisilazide, 337 Lithium B-isopinocampheyl-9-borabi-cycloj 3.3.1) -nonyl hydride, 303 Lithium N-isopropylcyclohexylamide, 169 Lithium o-lithiobenzylate, 67 Lithium (l-lithiopropionate, 303 Lithium methyl mercaptide, 303-304 Lithium methylthioformaldinc, 305 Lithium naphthalenide, 303, 305-306 Lithium perchlorate, 212 Lithium n-propylmercaptide, 283 Lithium selenophenolate, 306-307 Lithium 2,2,6,6-tetramethylpiperidide, 299, 307-308... 

Selective catalytic hydrogenation of the 6,7-double bond of 17/3-acetoxy-7-methylandrosta-4,6-dien-3-one was achieved with Pd-C-PhCH20H and gave the 7/8-methyl dihydro-compound. Added FeCls has been reported to improve the selectivity of reduction of a,/S-enones in metal-ammonia reactions, thereby improving the yield of the saturated ketones. Similar improvements were observed in the lithium-ethylamine reductions at -78 C when a substantial excess of lithium was used and t-butyl alcohol was the proton source. The influence of solvent and added nitrogenous bases on the stereoselectivity of hydrogenation of A - and A -3-oxo-steroids with Pd catalysts has been studied, and the stereoselectivity of Pd-catalysed hydrogenation of various A -7-oxo-steroids has been reported to be unaffected by substituents at C-3 or C-17. 

The easy isomerization of the sulphone-stabilizing anion generated from the phenyl sulphone (62) has been put to good use in a novel route to alk-2-enes (65) in reasonable yields (Scheme 15). The anion is alkylated stereo- and regio-specifically to give the a(S-unsaturated sulphone (63) on isomerization of the intermediate (64) with catalytic amounts of potassium t-butoxide. Small amounts of the a,a-dialkylated products are also formed. Reductive removal of the phenyl-sulphone moiety by lithium-ethylamine in the usual way, or better under milder conditions with potassium-graphite, gives the product. 

Tertiary alcohols can be conveniently deoxygenated in high yields through thiohydroxamic-O-esters. In practice, an oxalic acid half ester is prepared and decomposed in the presence of t-butylthiol or 1,1-diethylpropanethiol under radical conditions (equation 27). Diethyl phosphates and iV,A,N, AT -tetramethylphosphoro-diamidates of alcohols are readily reduced by lithium-ethylamine solutions. The method works well with both secondary and tertiary alcohols, the latter shown by the conversion of 1-adamantanol to adamantane (equation 28) °. 

There have been very few examples of 5,6-dihydro-a-pyrones isolated from the marine environment. In 1992, Hamada et al. obtained lobatrienolide (18) from an Okinawan soft coral Sinularia flexibilis (25). The structure of lobatrienolide was established by spectral techniques and confirmed by photo-oxidation of lobatriene (19), isolated from the same soft coral collection, to (18). The structure of (19) was proved as follows Scheme 1). Lithium-ethylamine reduction of (19) produced the diol (20) which on ozonolysis, MCPBA oxidation to the acetate (21) and hydrolysis gave the alcohol (22). The 5-stereochemistry of the alcoholic group in (22) was determined by the modified Mosher method 24), which together with NMR correlations in lobatriene, afforded the complete stereochemistry of (19) and hence also that of lobatrienolide... 

Lithium ethylamine Ethylene derivs. from alkoxy-2-ethylenes... 

Lithium ethylamine-tert butanol Hydrocarbons from phosphorodiamidates O PO(N < ... 

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