o-toluidine (1 equiv)
triethylamine (1 equiv)
pivaloyl chloride (1 equiv)
dichloromethane (0.6 mL/ mmol)
n-butyl lithium (1 equiv)
THF (5 mL/ mmol)

Procedure a: To a stirred solution of o-toluidine (10 g) and triethylamine (9.41 g) [not necessarily dry] in anhydrous DCM (50 mL) cooled to 0 ^oC was slowly added a solution of pivaloyl chloride (11.2 g) in anhydrous DCM (c.a. 10 mL/ 100 mmol). Upon complete addition stirring was continued for a further 30 minutes and then poured into water (200 mL). The organic layer was washed with water (3 x 100 mL) and dried over sodium sulphate. The crude white solid afforded on solvent evaporation was recrystallised twice from hot DCM / hexane (12/80 mL) to afford the title compound as a white solid. Yield 83 %. Procedure b: To a solution of N-pivaloyl-o-toluidene (70-100 mg) in anhydrous THF (c.a. 1 mL) in a flame dried, nitrogen flushed flask was slowly added n-BuLi [microsyringe] until a colour change was evident [bright yellow].

The indicator can be formed on a 10 g scale and is indefinitely air stable. The reference also identifies another indicator which can be prepared in an analogous fashion [N-pivaloyl-o-benzylaniline] and can again be used for titration of organolithium bases. These indicators are widely used for the titration of nBuLi but also show a colour change for tBuLi, sBuLi, MeLi and PhLi. On a practical point, the titration must be carried out under inert conditions or a false end-point may occur [i.e. yellow colour may disappear]. Also, the end-point is more readily observed if a filter paper is placed under the flask. Finally, the titration should be carried out three times, or until two concurrent results so as to receive an accurate molarity.

m.p 109-111 ^oC, 1H nmr (300 MHz, CDCl₃) 1.34 (9H, s), 2.27 (3H, s), 7.07 (1H, dd, J=7.5, 1.1Hz), 7.17 (1H, dd, J=7.5, 0.5Hz), 7.22 (1H, d, J=7.5Hz), 7.87 (1H, d, J=7.5Hz).

Jean Suffert; J. Org. Chem. 1989, 54, 509-510