54925-64-3Relevant articles and documents
Quassinoid Synthesis. 2. Preparation of a Tetracyclic Intermediate Having the Bruceantin Tetrahydrofuran Ring
Kerwin, Sean M.,Paul, Axel G.,Heathcock,Clayton H.
, p. 1686 - 1695 (1987)
A synthetic approach to the quassinoid compound bruceantin is described.Tricyclic acid 5, prepared from 2-(methoxycarbonyl)cyclohexanone in one step by the method of Fuchs, is converted into ketal lactone 6 and thence into diol 7.The primary hydroxyl may be selectively protected to give any of several derivatives, including the tetrahydropyranyl derivative 10.Allylic oxidation of this substance provides enone 13, which is dehydrated by treatment with 4-(dimethylamino)pyridine in refluxing acetic anhydride to obtain 16.Lithium/ammonia reduction of 16 yields saturated ketone 23, which is carboxylated by the Stiles procedure to obtain the enolic β- keto ester 26.This material is dehydrogenated to 28 by a novel procedure wherein the enol is heated with thionyl chloride and collidine in refluxing carbon tetrachloride.It is proposed that the dehydrogenation occurs by sulfenylation on carbon, followed by pyrolytic elimination of the resulting sulfenyl chloride ( Scheme III ).The elements of the eventual tetrahydropyranone ring are introduced at this stage by reaction of 28 with silyl ketene acetal 29 at high pressure.The product, enol silane 31, is deprotected by treatment with pyridinium p-toluenesulfonate in warm ethanol to obtain 39.Bromocyclization of this material upon treatment with N-bromosuccinimide in tetrahydrofuran affords bromo eter 40, which rearranges to tetrahydrofuran 41 upon being heated at reflux in N,N-dimethylformamide solution.Deprotection of the latter material provides the β-keto ester 42, a viable intermediate for a bruceantin synthesis.
Iodine-promoted silylation of alcohols with silyl chlorides. Synthetic and mechanistic studies
Bartoszewicz, Agnieszka,Kalek, Marcin,Stawinski, Jacek
, p. 8843 - 8850 (2008/12/21)
An efficient silylating system for 1°, 2°, and 3° alcohols, consisting of a silyl chloride/N-methylimidazole/iodine, was developed. Synthetic and mechanistic aspects of this new reagent system, and particularly the role of iodine were investigated in detail using 1H NMR spectroscopy.
Effective silylation of carboxylic acids under solvent-free conditions with tert-butyldimethylsilyl chloride (TBDMSCL) and triisopropylsilyl chloride (TIPSCL)
Firouzabadi, Habib,Iranpoor, Naser,Shaterian, Hamid Reza
, p. 71 - 81 (2007/10/03)
Varions types of carboxylic acids can be converted effectively to their corresponding TBDMS and TIPS esters using TBDMSCI and TIPSCI in the presence of imidazole under solvent-free conditions. The advantage of this modified method in comparison with that reported by Corey is the elimination of DMF, which eliminates aqueous work-up. The method is not a time-consuming process and the reactions proceed spontaneously. By this method, absolute chemoselectivity for the protection of carboxylic acid functions in the presence of 2°, 3° hydroxyl groups are observed.
