Adamantyl silica

We further synthesized unsymmetrical MiniPHOS derivatives 13b (Scheme 13) [30]. Thus, enantioselective deprotonation of l-adamantyl(dimethyl)phos-phine-borane (74, R = 1 -Ad), followed by treatment with ferf-butyldichlorophos-phine or 1-adamantyldichlorophosphine, methylmagnesium bromide and bo-rane-THF complex afforded the optically active diphosphine-boranes 82b as a mixture with the corresponding raeso-diastereomer. Enantiomerically pure unsymmetrical MiniPHOS-boranes 82b were obtained by column chromatography on silica gel or separation by recycling preparative HPLC. 

The solid acid catalyzed adamantylation of substituted benzene derivatives was studied with the aim to achieve high para regioselectivities. Of various acidic resins, zeolite HY, sulfated zirconia, perfluorolkanesulfonic acids, and phosphotungstic acid, Amberlyst XN-1010 was found to be the catalyst of choice to afford para-substituted alkylbenzenes with selectivities exceeding 70%.398 In further systematic studies with a Nafion-H-silica nanocomposite catalyst,399 and various... 

In a similar study, Nafion-H beads, 10% Nafion-H on silica, and 13% Nafion-silica were compared in the adamantylation of toluene with 1-bromoadamantane.239 13% Nafion-silica nanocomposite exhibited the highest activity and showed achangeinthe isomeric ratio of the two alkylated products the para/me ta ratio shifted to lower values in prolonged reaction (Table 5.20). Acidity is known to exert a significant influence on... 

To suspension of sodium hydride (80% in oil, 4.32 g, 144 mmol) in 50 ml of TFIF, there are slowly added while maintaining the temperature at 20°C, 36.8 g (120 mmol) of 2-(l-adamantyl)-4-bromophenol. The mixture is stirred for 1 hour at ambient temperature at which point 9 ml of methyl iodide are added. The mixture is then stirred for 2 hours at 20°C, poured into water, extracted with ether, dried and evaporated. The product is purified by passage through a silica column (10x30), eluting with a mixture of hexane (90%) and dichloromethane (10%). On evaporation, 26.2 g of a white solid are obtained. Yield - 68%. MP 138°-139°C. 

To a mixture of adamantyl bromide (0.5 mmol) and trifluoroacetate salt of lepidine (2.5 mmol) in benzene (6 ml) were added (trimethylsilyl)silane (1.0 mmol) and AIBN (1.0 mmol). The mixture was heated at 80 °C for 14 h under an argon atmosphere. After the reaction, the reaction mixture was washed with sat. aq. NaHC03. The organic layer was dried over Na2S04. After removal of the solvent, the residue was chromatographed on silica gel to give 2-(l-adamantyl)-4-methylquinoline in 90% (125 mg) yield [33]. 

All the yields were from good to excellent, with the exception of the compound bearing both /-butyl and 1-adamantyl groups, probably due to steric reasons. It has to be mentioned that a quick filtration of the reaction mixture through a short pad of silica gel was in general sufficient to afford pure crystalline materials. 

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