Lithium diisopropylamine

Pyrroline-A-oxide (258) is isomerized into y-lactam (259) in the presence of lithium diisopropylamine (LDA) (470) and sodium trityl (471). In these reactions, deprotonation at C3 occurs, leading to carbanion (260). Then oxygen migration from Ni to C2 takes place via intermediate formation of oxaziridine... 

For example, the reaction of lithium diisopropylamine (82) with N-oxide (134) leads to a rather selective deprotonation at the C-4 atom (Scheme 3.111, Eq. 1). An analogous transfer of double bond was observed for six-membered cyclic nitronates 135 (Eq. 2) (143). However, intermediates (136) that formed in the latter case undergo fast fragmentation and give conjugated ene-oximes (137) as the final products. 

The fused dicyclopropane (12) has been synthesized by treating nitrocyclopropane (11) with lithium diisopropylamine in THF at low temperature. ... 

Butyl lithium Diisopropylamine Methyl 3,3-dimethyl acrylate p-Ionylidene acetaldehyde... 

Lactone 7 (derived from D-isoascorbic acid) reacted readily with the aryllithium formed from bromide 8 to produce lactol 9 (Scheme 16.3). The latter underwent a facile ring-opening and Wittig olefination with methylenetriphenylphosphorane to give 6 in excellent overall yield. After 0-trifLation, a two-carbon chain extension was performed on 10 with the azaenolate derived from A-cyclohexylacetaldimine 11 and lithium diisopropylamine (LDA). After acid hydrolysis of the product imine, aldehyde 12 was isolated in 83% yield for the two steps. The (2-azaallyl)stannane 5 was prepared from aldehyde 12 in quantitative yield by treatment with (aminomethyl)tri-n-butylstannane. 

Lithium diisopropylamine (0.2 mol) dissolved in 300 ml THF at —20°C was added to ethyl 4-t-butylcyclohexylcarboxylate (0.2 mol), stirred 1 hour, and the temperature lowered to —70°C. Thereafter, allylbromide (0.2 mol) was added and the mixture allowed to come to ambient temperature overnight. The mixture was quenched with NH4CI solution, the organic layer concentrated, and the product distilled at 75-82 °C at 0.03 mbar and 46 g of product isolated as a colorless oil. 

In the fully conjugated homoporphyrin series, an anionic derivative, 4.33a, has also been produced. It was prepared by treating the Ni(II)-containing endo and exo isomers 4.16a and 4.16b with lithium diisopropylamine in THF (Scheme 4.1.15). This anionic nickel complex (4.33a) was not characterized extensively. However, it was noted that protonation with water or acetic acid affords 4.32a as the major product. 

First the hydroxy group is protected as the TBS ether. In the second step lithium diisopropylamine (EDA) is used to deprotonate the a-carbon and the resulting lithium enolate is trapped as trifluoro-methanesulfonic acid ester. In the last reaction, palladium catalysis is used to introduce the carbon monoxide. In the presence of methanol this intermediate directly yields the methyl ester. 

The standard Ireland conditions for the ester enolate rearrangement (lithium diisopropylamine, tetrahydrofuran) give a retro-Michael addition product in this ease. However, silyl ketene acetal 15 is successfully obtained by the silyl triflate/triethylamine protocol539 for the preparation of ketene acetals which proceeds via a silyladon and then deprotonation mechanism560-563. 

The metallation of a methyl group of PMe2R coordinated to a metal, leading to three-membered ring, occurs by the reaction with strong bases such as lithium diisopropylamine ... 

The preparation of thieno[3,2-fc]thiophene was reported by Iddon and co-workers [76, 77] and it is readily prepared in four steps from commercially available 3-bromothiophene (Scheme 17.1). Thus 3-bromo-thiophene can be lithiated in the 2-position with a bulky non-nucleophilic base such as lithium diisopropylamine. Quenching of the resulting thiophene anion with dimethylfonnamide or tV-formylpiperidine afforded the thiophene aldehyde. Treatment of this o-bromoaldehyde with ethyl 2-sulfanylacetate in the presence of base afforded thieno[3,2-fc]thiophene carboxylate ester in good yield. Hydrolysis of the ester group, followed by thermal decarboxylation of the resulting acid with quinoline in the presence of copper, afforded the unsubstituted thieno[3,2-f>]thiophene in overall yields of approximately 60 % over the four steps. 

Acidity of Terminai Aikynes (Section 7.4) Treatment of terminal alkynes 25) with a strong base [most commonly NaNHj, NaH, or lithium diisopropylamine (LDA)] gives an acetylide salt. 

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