Methyl iodide → Lithium Hexamethyldisilazide

Participants

Reaction Steps

Lithium hexamethyldisilazide was prepared by addition of 1.24 ml of 1.55 M BuLi-hexane solution at −40° C. to a solution of 0.44 ml of bistrimethylsilylamine in 4 ml of THF. After stirring for ½ h a solution of 0.56 g of 59 and 0.46 ml of DMPU in 8 ml of THF was added. Stirring was continued for 45 min at −40° C. followed by addition of 140 μl of methyliodide. Upon stirring for an additional 30 min the alkylation was complete. The mixture was poured into 40 ml of sat NH4Cl solution and extracted with ethyl acetate. Chromatographic purification provided 0.55 g of 16α-methylated product 60. Rf 0.73 (hept/ethyl ac. 1/1)starting material Rf 0.69; NMR δ 1.11 (d, 3, 16αCH3), 1.02 (s, 3, 18CH3), 0.82 (d, 3, 7αCH3), 0.91 (d, 3, 11βCH3).

Provenance & Evidence