Benzoic acid, 2-ethyl-4-Methoxy-3-Methyl- synthesis

Yield:1181770-76-2 91%

Reaction Conditions:

Stage #1: 4-methoxy-2,3-dimethyl-benzoic acidwith sec.-butyllithium in tetrahydrofuran;cyclohexane at -78; for 1 h;Inert atmosphere;
Stage #2: methyl iodide in tetrahydrofuran;cyclohexane at -78; for 1 h;
Stage #3: with hydrogenchloride;water at 0; pH=1; for 0.5 h;

Steps:

B1

2-Ethyl-4-methoxy-3-methylbenzoic acid 20.0 g of 4-methoxy-2,3-dimethylbenzoic acid (C1) are dissolved in one litre of tetrahydrofuran in a dry nitrogen atmosphere and subsequently cooled to -78° C. 300 ml of sec-butyllithium (1.4 M in cyclohexane) are then added dropwise to give a red solution. The red solution is stirred at -78° C. for a further hour. 34.5 ml of methyl iodide are then added, and the resultant suspension is stirred for one hour without cooling. 300 ml of water are subsequently added, and the solution is extracted, using ethyl acetate, twice with 300 ml of ethyl acetate each time. The aqueous phase is subsequently filtered, the filtrate is cooled in an ice bath, adjusted to pH 1 by addition of hydrochloric acid (3.0 M) and stirred for a further 30 minutes. The suspension is then filtered and washed with water. The filter cake is dried at 110° C. in vacuo, giving 20.9 g of the title compound as colourless solid having a melting point of 180° C. (MS: 195.2 (MH⁺)).

References:

US2011/60050,2011,A1 Location in patent:Page/Page column 4