Allyl bromide → Methyl 2,3,3-trimethylbutanoate

Beteiligte Stoffe

Reaktionsschritte

A solution of lithium diisopropylamide was prepared by treating diisopropylamine (40.91 g, 405 mmol) in dry THF (350 mL) with butyllithium in hexanes (2.5 M, 154.4 mL, 386 mmol) at 0° C. for 15 min in a nitrogen atmosphere. Then a solution of methyl 2,3,3-trimethylbutyrate (38.88 g, 270 mmol) in THF (30 mL) was added slowly, and the mixture was stirred. Methyl 2,3,3-trimethylbutyrate was prepared as in Quast H, Meichsner G, Seiferling B (1986) "Photochemical formation of methylenecyclopropane analogs. XII. Synthesis of 3,5,5-trialkyl-3,5-dihydro-4H-1,2,3-triazol-4-ones" Liebigs. Ann. Chem., 1891-1899. After 45 min. of stirring, the temperature of the mixture was reduced to -78° C. and a solution of allyl bromide (51.30 g, 424 mmol) in THF (20 mL) and HMPA (40.3 mL, 232 mmol) was added over a period of 15 min. Stirring was continued for 2 h at -78° C. and the system was allowed to warm to room temperature (ca. 6 h). The reaction was quenched by addition of HCl (3 N, 300 mL) at 0° C. The layers were separated and the aqueous phase was further extracted with ether (3×150 mL). The combined organic extract was washed sequentially with 100 mL portions of water, 5% Na2S2O3, saturated NaHCO3, water, and brine, and dried over MgSO4. The solvent was removed in vacuo to give 48.88 g of brown colored liquid, which upon two vacuum distillations, afforded olefinic ester (34.85 g, 70%) as a colorless liquid: bp 87-89° C. (20 mmHg).

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