C([Br:3])C.[Mg:4].[CH3:5][C:6]#[CH:7].[CH3:8][C@H:9]([CH2:13][CH2:14][CH2:15][CH:16]([CH3:18])[CH3:17])[CH2:10][CH:11]=[O:12].[NH4+].[Cl-]>C(OCC)C.O>[C:7]([Mg:4][Br:3])#[C:6][CH3:5].[CH3:8][C@H:9]([CH2:13][CH2:14][CH2:15][CH:16]([CH3:18])[CH3:17])[CH2:10][CH:11]([OH:12])[C:5]#[C:6][CH3:7]Propynyl magnesium bromide was prepared as described earlier from ethyl bromide (77 g, 0.405 mol, freshly distilled), magnesium (10.8 g 0.4455 mol) and methyl acetylene (approximately 100 ml at -70°) in 400 ml of absolute diethyl ether. To this well stirred mixture was added dropwise 26.4 g (0.169 mol) of 3(R),7-dimethyloctanal (R-(+)-dihydrocitronellal) in 500 ml of dry ether while the reaction temperature was maintained between 0°-5° C. with external cooling. After 45 min. all aldehyde had been added and the reaction was allowed to warm to 30° and stirred at this temperature for 1.0 hr. Thin layer chromatography analysis of the reaction mixture at this point showed the disappearance of starting material. The flask was then cooled in an ice-bath and 100 g of NH4Cl in 600 ml of water was added slowly. The content was transferred to a separatory funnel and the layers separated. The aqueous phase was further extracted with ether (3×250 ml). The combined ether extract was filtered quickly through Celite and washed with saturated brine (3×500 ml) and dried over MgSO4. After filtration the solvent was evaporated to dryness in a rotary evaporator (40°/25 mmHg) to give 33.1 g (100%) of crude 6(R),10-dimethyl-undecan-2-yn-4(R,S)-ol as a clear light amber oil.
読み込み中…
