Lithium carboxylate

A variation of this transfonnation reacts the acid with hthium naphthalenide in the presence of 1-chlorobutane. The product is the ketone. A related reaction treats the lithium carboxylate with lithium metal and the alkyl halide, with sonication, to give the ketone. ... 

Reaction between lithium carboxylates and alkyllithium compounds... 

G. Chimed and F. Masamichi, A lithium carboxylate ultrathin film on an aluminum cathode for enhanced electron injection in organic electroluminescent devices, Jpn. J. Appl. Phys., Part 2, 38 L1348-L1350 (1999). 

An extension of the Barbier reaction to carboxylates salts [90] affords a simple access to furanyl ketones [91]. By sonication of a mixture of a lithium carboxylate, an alkyl chloride and lithium in THE at room temperature, the intermediate organolithium reagent forms rapidly, then generates the 2-furanyl lithium which adds to the carboxylate group in high yields. The method constitutes an example of a reaction cascade , in which several intermediates are generated sequentially (Scheme 3.13). 

The reaction is believed to proceed by the indicated conversion of a lithium carboxylate to the dilithium salt which is stable... 

The attempt to use these salts originated from the hope that their dissociation constants would be high even in low dielectric media, and the organic nature of perfluorinated alkyls would always assist the solubility of the salts in nonaqueous solvents. Because of the requirement for electrochemical stability, lithium carboxylates (RF-C02Li, where Rp- = perfluorinated alkyls) are excluded from consideration, because their oxidation still occurs at - 3.5 V vs lithium, which is similar to the cases of their non-fluorinated counterparts. Obviously, the electron-withdrawing groups do not stabilize the carboxylate anions sufficiently to alter their oxidative stability. 

So far the only removable N-substituent to have been investigated with this system is the lithium carboxylate group, but instead of lithiation at the 6-position as expected, C-4 lithiation was observed (Scheme 121) (87T2343). Reaction with a variety of electrophiles occurred in moderate to good yield. 

Reaction at the C-l position has been achieved with a variety of electrophiles including carbon dioxide (44JA625), lithium carboxylates (60BSF1049), dialkylamides (82JHC433), and dihaloalkanes (83SC467). 

Step 4c Protonation of the lithium carboxylate and acetal hydrolysis. 

Aldimines can be trifluoromethylated at the imine carbon using Me3SiCF3 in dimethyl formamide at —20 °C, using a lithium carboxylate as catalyst.71 It is proposed that the carbon-silicon bond of the reagent is activated via formation of a lithium silicate bearing carboxylate and DMF ligands on silicon. A similar process has been used for diastereoselective addition to sulftnylimims.12... 

Crossed aldol reaction between an aromatic aldehyde and the TMS enolate of another aldehyde proceeds smoothly in wet or dry DMF using a lithium carboxylate as Lewis base catalyst.158 One-pot conversion to 1,3-diols using sodium borohydride as reductant gives up to 87% yield. A similar report, using tetrabutylammonium phe-nolates as Lewis bases, is diaslereoselective.159... 

An intramolecular 2-alkylation was also observed in a sulfonyl free radical induced addition-cyclization <95SL763>. A key intermediate in a new synthesis of pallescensin A (a biologically active labdane diterpene) was prepared by a cationic cyclization reaction with a furan <95SYN1141>. The sonochemical Barbier reaction was extended to carboxylate salts. 2-Furanylketones 10 can be obtained by sonication of a mixture of furan, lithium carboxylate, an alkylchloride, and lithium in THF <95JOC8>. 

Fig. 6.45. Chemoselective acylation of organolithium compounds with lithium-carboxylates (A). In order to generate the substrates the choice is between the deprotonation of the corresponding carboxylic acid and the addition of an organolithium compound to carbon dioxide, i.e. via C,C bond formation.

Lithium amides (LiTMP) can give good yields of products resulting from ortholithiation of both ketones and lithium carboxylates. Benzophenone 288, for example, with LiTMP gives a good yield of the ortholithiation-dimerisation product 289.103 In general, however, ketones and aldehydes are best lithiated by the method developed by Comins described in section 2.3.2.1.2. 

In an unconventional cyclopentenone synthesis, Negishi cyclised vinyllithiums derived from the 1-iodo- 1-silyl alkenes 103 onto preformed lithium carboxylate salts.57 He later found58 that amides 104 function in this reaction rather better than the carboxylate salts, and that the silyl substituent is not necessary for cyclisation. Nitriles, on the other hand, fail to cyclise. 

Several paths are possible for the rest of the mechanism. In one likely path, A1H3 adds to the carbonyl group of the lithium carboxylate salt. 

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