The cerium (III) mediated reaction of trimethylsilylmethyl magnesium chloride with esters and lactones: The efficient synthesis of some functionalised allylsilanes of use in annulation reactions
✍ Scribed by Thomas V. Lee; Julia A. Channon; Carmel Cregg; John R. Porter; Frances S. Roden; Helena T-L. Yeoh
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- French
- Weight
- 714 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
The use of cerium (Ill) chloride alters the chemoselectivity of the reaction of trimethylsilybnethyl magnesium chloride with ester-acetals and also greatly improves the e#iciency of reaction with lactones. In addition it gives improved preparations of the uqtiil intermediates (
), ( ), ( ),( ) and (22) and gives direct access to the valuable finctionalised allylsilanes (I) to (3) of use in annulation reactions. T. V. LEE et al. nitrogen for 19h. The dark brown mixture was cooled, diluted with diethyl ether (30ml) and Eltemd thmugh a bed of dry flash silica gel. Evaporation of the filtrate in vacua gave the same aldehyde as above aldehyde (O.lOg, 100%) which was used without further pmilication. Dry methanol (22ml). trimthylorthofotmate (44ml) and collidinium p-toluene sulphonate (O.Olg) were added to crude aldehyde ftom either of the above nactions and the pale yellow solution was heated at reflux under nitrogen for 12h. The naction was cooled to mom temperatum, evaporated in vacua to a low volume and diluted with diethyl ether (SOml). 'Ihe orgsnic phase was washed with saturated sodium hydrogencarbonate solution (lOml), brine (1Oml) and dried (MgSo4). Evaporation afforded the crude acetal (31) as a pale yellow oil (0.93g). Purification by w flash chromatography, eluting with petrol/ether (41) gave the acetal(3) as a colourless liquid (56%) RF 0.6. Found: C, 61.07; II, 11.31. CttH~O$i mquims C,