Dimethylformamide → 7-Bromo-9,9-diethylfluorene-2-carboxaldehyde

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a mechanically stirred solution of 9,9-diethyl-2,7-dibromofluorene (59.38 g., 0.1563 mol.), in THF (325 ml), cooled in dry ice-ethanol bath, n-butyl lithium (104 ml of 1.6M solution in hexanes, 0.1664 mol, 1.06 eq.) was added dropwise over 25 minutes. After 20 minutes, DMF (17 ml, 0.22 mol.) in THF (30 ml) was added, and the mixture was stirred in the cooling bath for 1.5 hours, and outside the bath for 1 hour. The reaction was then cooled to 5° C., and treated with hydrochloric acid (12.5 ml of concentrated hydrochloric acid diluted with 50 ml water). The mixture was diluted with 200 ml of toluene, and the aqueous phase was separated and extracted with 200 ml of toluene. The combined organic phase was washed with dilute sodium bicarbonate solution, dried over magnesium sulfate and concentrated. The residual solids were recrystallized from heptane -ethyl acetate (9:1), to get colorless solids, 40.29 g. (78.4% yield) m.p. 126-128° C. The mother liquor after chromatography over 150 g. silicagel, elution with 1:1 heptane-toluene, and trituration of residual solids in hexanes gave additional product, 6.56 g. (12.8% yield, total 91% yield), m.p. 126-128° C. Mass Spec: (m/z) 328,330, (M+). A sample for analysis was prepared by recrystallization from hexanes, m.p. 127-129° C. Anal: Calcd for C18H17BrO: C, 65.55; H, 5.20; and Br, 24.27. Found: C, 65.60; H, 5.51; and Br, 24.71.

Herkunft & Nachweise