Diisopropylamine → Lithium diisopropylamide

Participants

Reaction Steps

A LDA solution was prepared by adding at 0° 9.79 ml of nBuLi (1.55 M, hexane) to 2.30 ml of diisopropylamine. After cooling to -78°, 2.872 g of (E)-4-(dimethoxy-phosphoryl)-but-2-enoic acid methyl ester, dissolved in 17 ml of abs. THF, were added. 90 minutes later, 2.424 g of (R)-3-[(4aR,5S,8aS)-5-(tert-butyldimethyl-silanyloxy)-8a-methyl-3,4,4a,5,6,7,8,8a-octahydro-naphthalen-1-yl]-butyraldehyde dissolved in 15 ml of abs. THF, were added and allowed to react for 2 h at -78° and 1.5 h at -40°. The mixture was then poured onto crushed ice/NH4Cl, extracted with ether, washed with brine, dried over magnesium sulfate, and evaporated to dryness. Flash chromatography (SiO2, hexane/AcOEt=97/3), followed by MPLC (SiO2, hexane/AcOEt=98.9/1.9) and crystallization from hexane, yielded 1.367 g of (2E,4E)-(R)-7-[(4aR,5S,8aS)-5-(tert-butyldimethyl-silanyloxy)-8a-methyl-3,4,4a,5,6,7,8,8a-octahydro-naphthalen-1-yl]-octa-2,4-dienoic acid methyl ester as white crystals of mp. 59-64°.

Provenance & Evidence