1-Trimethylsilyloxy cyclohexene

Trimethylsilyloxy-cyclohexen reagiert mit Nitronimn-tetrafluoroborat in Acetonitril bei — 25° mit 47% Ausbeute zu 2-Nitro-l-oxo-cyclohexan2 (mit Nitryl-chlorid wird dagegen... 

Induziert durch einen OberschuB an Dichlor-diisopropyloxy-titan reagieren verschiedene -Nitro-1-alkene mit 1-Trimethylsilyloxy-cyclohexen in Dichlormethan bei — 90° zu bicyclischen Nitronaten, die mit katalytischen Mengen an Kaliuinfluorid in Methanol anti- bzw., syrt-2-(2-Nitro-ethyl)-l-oxo-cyclohexane liefem (55-81%)4 ... 

The analogous reaction with 1,1,3-trimethyl-2-(trimethylsilyloxy)cyclohexene employing titani-um(IV) as the Lewis acid also proceeded in the same stereochemical sense and gave 1,2-benzox-azin-2-ium 2-oxide 6 as the only diastereomeric product in 75% yield16. 

A mixture of finely ground benzyltrimethylammonium fluoride (125 mmol) and molecular sieves (50 g, 4 A) in THF (50 ml) was stirred for 14 h at ambient temperature, and then the mixture was cooled to 0°C. A solution of l-(trimethylsilyloxy)cyclohexene (115 mmol) and methyl bromoacetate (105 mmol) in THF (50 ml) was added with stirring over 10 min. After stirring for a further 10 min at 0 °C, stirring was continued for 11 h at ambient temperature. The reaction mixture was filtered through Celite. concentrated and distilled, to give the ketoester (75 mmol, 65%), b.p. 90-100°C/1.2mmHg. 

Ausgehend von 3-Methyl-2-trimethylsilyloxy-cyclohexen wird zu 47% ein cis/trans-Ge-misch (30 70) von 6-Methyl-2-ntiro-l-oxo-cyclohexan erhalten5 ... 

In analoger Weise erhalt man aus l,3-Dimethyl-2-trimethylsilyloxy-cyclohexen 2,6-Dime-thyl-2-nitro-l-oxo-cyclohexan (41%) bzw. aus 1-Trimethylsilyloxy-cyclopenten 2-Nitro-l-oxo-cyclopentan2 (95%). 

Die Regioselektivitat dieser Art von Aminomethylierung zeigt sich z. B. auch bei den Re-aktionen von 2-Methyl-l-trimethylsilyloxy-cyclohexen und von 4a-Methyl-2-trimethyl-silyloxy-3,4,4a,5,6,7-hexahydro-naphthalin mit N,N-Dimethyl-methaniminium-jodid, welche unter ausschlieBlicher Bildung von 2-(Dimethylammo-methyl)-2-methyl-l-oxo-cy-clohexan (65%) bzw. 8-(Dimethylamino-methyl)-4u.-methyl-2-oxo-2,3,4,4a,5,6,7,8-octa-hydro-naphthalin (65%) verlaufen1. 

It should be noted that several procedures are available for the preparation of l-(trimethylsilyloxy)cyclohexene. In an original report252 it was prepared by heating a dimethylformamide solution of cyclohexanone under reflux with chlorotrimethylsilane in the presence of triethylamine. This procedure is generally satisfactory for aldehydes and symmetrical ketones, or ketones which can enolise in one direction only. The method described in Expt 5.214 employs lithium sulphide as an additive to increase the silylating power of the chlorotrimethylsilane, so that the reaction proceeds at room temperature acetonitrile is used as the solvent.253... 

Alkylation of l-(trimethylsilyloxy)cyclohexene with hexacarbonyl-(l-methyl-2-propynylium)dicobalt tetrafluoroborate. 

Enol silyl ethers react with aldehydes with a catalytic amount of TBAF to give the aldol silyl ethers in good yields. These reactions generally proceed under very mild conditions and within shorter periods of time than conventional strong acidic or basic conditions. The products from4-f-butyl-l-methyl-2-(trimethylsilyloxy) cyclohexene and benzaldehyde show very good axial selectivity and a little anti-syn selectivity (eq 20). The aldol condensation of ketones and aldehydes can be achieved in one pot when ethyl (trimethylsilyl)acetate is used as a silylation agent with TBAF (eq 21). 

Maruoka and Ooi reported that a significant activation of carbonyl reactivity can be realized through the double coordination of carbonyl compounds by appropriate bidentate Lewis acids such as aluminum Lewis acid (17) prepared by treatment of the biphenylenediol (18) with Me3Al (2 equivalent) in CH2CI2 at room temperature for 30 minutes. The Mukaiyama aldol reaction of l-(trimethylsilyloxy)- -cyclohexene with benzaldehyde is effected by this bidentate Lewis acid (17) to give the aldol products in 87% yield (erythro/threo = 1 3). On the other hand, the use of its monodentate counterpart (19) did not produce the aldol products under similar conditions (Scheme 6.19). [26] Another examples of the carbonyl activation by bidentate aluminum Lewis acids are summarized in Section 6.6. 

To a solution of acetyl chloride (0.79 g, 10 mmol) and TiCU (19 g, 10 nunol) in CH2CI2 (15 mL) is added 2-methyl-l-(trimethylsilyloxy)- -cyclohexene (1.8 g, 10 mmol) in CH2CI2 (8 mL) at -78 °C over 15 min. After being stirred at -78 °C for 1 h, the reaction mixture is warmed slowly to rt over 2 h and diluted with diethyl ether (20 mL). The whole is poured into saturated NaHCOa aq. Standard workup followed by column chromatography on silica gel gives the title compound in 91% yield. ... 

Ethyl 3-[3-(trimethylsilyloxy)cyclohex-2-enyl)]propionate 2-Cyclohexene-l-propanoic acid, 3-[(trimethylsilyl)oxy]-, ethyl ester (11) (90147-64-1)... 

TRIMETHYLSILYLOXY-l,3-BUTADIENE AS A REACTIVE DIENE DIETHYL traits-4-TRIMETHYLSILYLOXY-4-CYCLOHEXENE-l,2-DICARBOXYLATE... 

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