Displacements from acetals, aminals, orthoesters and related compounds

2 Displacements from acetals, aminals, orthoesters and related compounds 

Under mild conditions, acetals are sufficiently unreactive towards organomagnesium compounds to serve as protected carbonyl compounds. Under more vigorous conditions, however, displacement of one alkoxy group occurs  

The paper in which the following procedure was described reports several other examples [10], and references to others are given in a review [11] see also Ref. [12]. 

Isopropylmagnesium bromide (2.5 M in ether, 0.36 ml) is added to a solution of (lS,2/ ,4/ )-2-(2-methoxyethoxy)methoxy)-6-methylene-bicyclo[2.2.2]octane (68 mg, 0.3 mmol) in toluene (2.0 ml). The mixture is heated under reflux for 15 min (during which time a white precipitate forms). The mixture is cooled to room temperature, and water (10 ml) is added. The product is isolated via ether extraction (X3), chromatography and Kugelrohr distillation (150-160°/30 torr) as a colourless oil (47.2 mg, 81%). 

In analogous reaction of aminals, alkoxy rather than dialkylamino groups are normally displaced (for an exception, see Section 8.3.1)  

---