Lithium Carbonate

Li2CO3

[554-13-2]  · CLi2O3  · Lithium Carbonate  · (MW 73.89)

(base for dehydrohalogenation reactions and halide displacements; reagent for regioselective alkylations)

Physical Data: mp 723 °C; bp 1310 °C; d 2.11 g cm-3.

Solubility: sol cold (1 g/78 mL), hot H2O (1 g/140 mL); insol alcohol, acetone.

Form Supplied in: white powder; widely available. Drying: details are available.1

Dehydrohalogenation.

Lithium carbonate in refluxing DMF is an excellent base for dehydrohalogenation reactions. LiCl in DMF caused rearrangement of the alkene to the more substituted a,b-position.2 Treatment with a stronger base, lithium carbonate, led to good yields of the less substituted enone (eq 1). Substituted tropones have been prepared in a similar manner from alkyl-substituted tribrominated cycloheptanones (eq 2).3

Halide Displacement.

A preparation of steroidal oxetanones has been reported using Li2CO3 in refluxing DMF. It was found that either the cis or the trans bromides can give the a-oxetanone in good yield (eq 3).4

Alkylations.

Lithium carbonate used in conjunction with DMF and various alkylating agents has been found to regioselectively alkylate bisphenolic, 1,3-dicarbonyl, and thiol substrates that contain hydrogens that are more acidic than phenol (pKa &AApprox; 8).5 It has been determined that phenolic compounds containing electron-withdrawing groups alkylate at either the ortho or para positions exclusively (eq 4). Attempts to use other bases such as Potassium Carbonate or Sodium Carbonate showed a loss of selectivity. Using more reactive alkylating agents such as propargyl bromide (see under Propargyl Chloride) or Benzyl Bromide also reduces the selectivity of alkylation. This sequence has been used to differentiate between the two hydroxyl groups present in alizarin (eq 5).5

1,3-Dicarbonyl compounds such as b-keto esters or b-diketones are sufficiently acidic to alkylate as well (eq 6).5

Thiophenoxyphenols have shown selectivity of alkylation with lithium carbonate. The more acidic S-H can be preferentially alkylated in deference to a phenolic O-H bond.5 Using potassium carbonate in the same alkylation scheme gives only 4% of the desired product.

Base Assistance.

Spirocyclic ethers can be generated via intramolecular nucleophilic attack of hydroxide upon p-(allyl)palladium complexes (eq 7). The attack of an external nucleophile can then be directed for either cis or trans addition, depending on the concentration of nucleophile present.6 In the presence of 3 equiv of Li2CO3, cis migration of acetate was the only reaction observed. Conversely, the addition of 1.8 equiv of chloride ion causes chloride to be added from the face opposite the metal.

Related Reagents.

Lithium Carbonate-Lithium Bromide; Potassium Carbonate; Sodium Carbonate.


1. Inorg. Synth. 1939, 1, 1.
2. House, H. O.; Bashe, R. W. II. JOC 1965, 30, 2942.
3. (a) Jones, G. JCS(C) 1970, 1230. (b) Collington, E. W.; Jones, G. JCS(C) 1969, 2656. (c) Collington, E. W.; Jones, G. CC 1968, 958.
4. (a) Hanna, R.; Maalouf, G.; Muckensturm, B. T 1973, 29, 2297. (b) Rowland, A. T.; Bennett, R. J.; Shoupe, T. S. JOC 1968, 33, 2426.
5. Wymann, W. E.; Davis, R.; Patterson, J. W.; Pfister, J. SC 1988, 18, 1379.
6. Bäckvall, J. E.; Andersson, P. G. JOC 1991, 56, 2274.

Dennis Wright & Mark C. McMills

Ohio University, Athens, OH, USA



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