Lithium imides preparation

Lithium Amide. Lithium amide [7782-89-0], LiNH2, is produced from the reaction of anhydrous ammonia and lithium hydride. The compound can also be prepared by the removal of ammonia from solutions of lithium metal in the presence of catalysts (54). Lithium amide starts to decompose at 320°C and melts at 375°C. Decomposition of the amide above 400°C results first in lithium imide, Li2NH, and eventually in lithium nitride, Li N. Lithium amide is used in the production of antioxidants (qv) and antihistamines (see HiSTAMlNE AND HISTAMINE ANTAGONISTS). 

Imidate esters can also be generated by reaction of imidoyl chlorides and allylic alcohols. The lithium anions of these imidates, prepared using lithium diethylamide, rearrange at around 0°C. When a chiral amine is used, this reaction can give rise to enantioselective formation of 7, 8-unsaturated amides. Good results were obtained with a chiral binaphthylamine.265 The methoxy substituent is believed to play a role as a Li+ ligand in the reactive enolate. 

Lithium amides and lithium imides (iminolithiums) (R2C=NLi) have also been used to prepare amides and imides of other metals and... 

Guntz recommends the formation of the nitride as a convenient means of isolating argon,9 and its interaction with metallic chlorides as a method for preparing other nitrides.10 For the heat of formation he found 49 5 Cal.11 It is formed by the action of light on lithium imide, LigNH (p. 72) 12... 

Metal amides can be added to ordinary nitriles e.g. lithium, sodium or magnesium amides), thus forming amide imide salts, which on addition of water or alcohol afford amidines. Some recent results demonstrate the wide applicability of the method, e.g. from metal amides and trialkoxyacetonitriles, tri-alkoxyacetamidines (319 Scheme 52) were prepared and from lithium imides and nitriles A -alkylide-neamidines (320) could be synthesized. 

Lithium imides (imidolithiums) are air-sensitive compounds of general formula (RR C=NLi) . They can be prepared in high yield either by the addition of an organolithium compound across the triple bond of a nitrile (equation (1)) or by lithiation of a ketimine (equation (2)). 

Nitta, Hatanaka and Ishimura11 started their synthesis of cephalosporin precursors from L-aspartic acid. The key intermediate is the lactone 1. The azidation resembles the general preparation procedure given for open-chain imide enolates in Section 7.1.1. The main differences are the generation of a dianion with lithium diisopropylamide and the application of tosyl azide. 

Hydroxymethylpyrazines may be prepared by reduction of carboxylic acid derivatives. Thus reduction of 2-amino-3-methoxycarbonylpyrazine with lithium aluminum hydride in tetrahydrofuran gave 2-amino-3-hydroxymethylpyrazine (1074, 1075) the imide from 23-dicarboxypyrazine (20) with sodium borohydride in tetrahydrofuran gave 2-carbamoyl-3-hydroxymethylpyrazine (21), and the methylcarbamoyl analogue was prepared similarly (1076). 

On the other hand, Carreira et al. also reported the total synthesis of trehazolin from the optically active spirocycloheptadiene [196], which was prepared from the (7 )-epichlorohydrin 282 and lithium cyclopentadienide, shown in O Scheme 41. Treatment of lithium cyclopentadi-enide (CpH+BuLi) with (/J)-epichlorohydrin 282 afforded the optically active spirocycloheptadiene 283 in 91% ee. Compound 283 was converted into trichloroacetimidate 284 by treatment of NaH and CI3CCN [197], and subsequent treatment of 284 with I(. -cohidine)2C104 gave the alcohol 287 via the unstable intermediates 285 and 286. After silylation of the secondary hydroxy group of 287, the imidate underwent nucleophilic opening upon treatment of the corresponding silyl-protected imidate with Li2NiBr4 to yield the cyclopropylcarbinyl bro-... 

For the synthesis of (69), the enol ether (71) from the indanone (70) was carboxylated with COa-n-butyl-Iithium in THF at —70 C to yield (72). The methyl ester (73) was converted into (75) via the maleic anhydride adduct (74), essentially as described in earlier work. Lithium aluminium hydride reduction followed by oxidation with dicyclohexylcarbodi-imide afforded the aldehyde (76). This was condensed with excess (77) to yield a mixture of the diastereomers (78). Oxidation with chromium trioxide-pyridine in methylene dichloride gave (79), which could be converted into the diketone (80) by treatment with excess benzenesulphonylazide. The diketo-lactam (81) was prepared from (80) as described for the synthesis of the analogous intermediate used in the synthesis of napelline. Reduction of (81) with lithium tri-t butoxyaluminohydride gave the desired dihydroxy-lactam (82). Methylation of (82) with methyl iodide-sodium hydride gave (83). Reduction of this lactam to the amine (84) with lithium aluminium hydride, followed by oxidation with potassium permanganate in acetic acid, gave (69). 

As shown in Scheme 9-57, the Ci-Cf, ketones 202 and 203 have both been prepared by aldol chemistry. The synthesis of ketone 202 used the Braun auxiliary 204 in a lithium-mediated aldol reaction and afforded adduct 205 in 75% yield and 98% ds [75]. This synthe.sis can be compared with the related Reformatsky reaction of imide 206, again controlled by an auxiliary attached to the enolate... 

Our research group independently found a catalytic enantioselective proto-nation of preformed enolate 47 with (S,S)-imide 30 founded on a similar concept (Scheme 5) [51]. The chiral imide 30, which has an asymmetric 2-oxazoline ring and is easily prepared from Kemp s triacid and optically active amino alcohol, is an efficient chiral proton source for asymmetric transformation of simple metal enolates into the corresponding optically active ketones [50]. When the lithium enolate 47 was treated with a stoichiometric amount of the imide 30, (K)-en-riched ketone 48 was produced with 87% ee. By a H-NMR experiment of a mixture of (S,S)-imide 30 and lithium bromide, the chiral imide 30 was found to form a complex rapidly with the lithium salt. We envisaged that a catalytic asym-... 

Approaches to modifying materials for the second (imide-amide) stage of the Li-N-H cycle have been varied. Hu and Ruckenstein considered the effect of preparative route on the storage performance of Li2NH by contrasting the usual method of amide decomposition (with or without hydride addition, equations 16.7 and 16.8) with both the action of ammonia on lithium (Eq. 

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