Ethyl 3,3-diethoxypropionate → Ethyl 2-(6-bromoisochroman-1-yl)acetate

Reaktionsgleichung

[Br:1][C:2]1[CH:3]=[C:4]([CH2:8][CH2:9][OH:10])[CH:5]=[CH:6][CH:7]=1.[CH2:11]([O:13][CH:14]([O:21]CC)[CH2:15][C:16](OCC)=O)[CH3:12]>[N+](C)([O-])=O.[Ti](Cl)(Cl)(Cl)Cl>[Br:1][C:2]1[CH:3]=[C:4]2[C:5](=[CH:6][CH:7]=1)[CH:16]([CH2:15][C:14]([O:13][CH2:11][CH3:12])=[O:21])[O:10][CH2:9][CH2:8]2

Komponenten

Versuchsvorschrift

Titanium tetrachloride (1M in methylene chloride, 51 ml) is added over a period of 10 min to an ice-cooled mixture of 2-(3-bromophenyl)ethanol (XLV, 4.34 g, 21.6 mmol) and ethyl 3,3-diethoxypropionate (LXXXV, 4.93 g, 25.9 mmol) in nitromethane (5 ml). After stirring for 10 min, the ice bath is removed and the mixture is allowed to stir at 20-250 for 5 hr, at which time it is poured onto ice/aqueous hydrochloric acid (~1N). The mixture is extracted with dichloromethane and backwashed with hydrochloric acid (0.5N)/saline and saline. The organic phase is separated dried over sodium sulfate, concentrated, and the residue chromatographed on silica gel eluting with ethyl acetate/hexane (5/95). The appropriate fractions are pooled and concentrated to give ethyl (6-bromoisochroman-1-yl)acetate (LXXVII), NMR (CDCl3) 1.28, 2.66-2.87, 2.96, 3.768, 3.807, 4.11, 4.21, 5.19, 6.93 and 7.28 δ.