Bis-(trialkylsilyl) phosphonates

Summary Methods of synthesis of the previously unknown bis-(trialkylsilyil) phosphonates were developed on the basis of reaction of phosphorous acid with trialkylchlorosilanes or trialkylalkoxysilanes. Their Raman spectra were studied.     

Five-coordinate hydrido / olefin platinum(II) complexes

Stable five-coordinate hydrido / olefin complexes of general formula [Pt(2,9-Me₂-1,10-phenanthroline)H(Cl)(olefin)] have been synthesized in high yield through oxidative addition of HCl to [Pt(2,9-Me₂-1,10-phenanthroline)(olefin)] precursors. Relevant spectroscopic features and some preliminary results concerning the reactivity of the new compounds are also reported.     

Simple and practical routes to enantiomerically pure 5-(trialkylsilyl)-2-cyclohexenones

[reaction: see text] Enantiomerically pure chiral 5-silylated 2-cyclohexenones are easily prepared in high yield using as a key step kinetic resolution with a commercially available lipase. Fully active enzyme can be recovered very efficiently for reuse. The synthetic steps are outlined in Schemes 1 and 3. Enantiomerically pure 2-cyclohexenones such as 1 and 2 are versatile intermediates for the synthesis of a multitude of chiral targets by means of a variety of diastereoselective reactions such as those illustrated in Scheme 2.     

Facile O-H bond activation in alcohols by [Cp*RuCl((I)Pr2PSX)] (X = pyridyl, quinolyl): a route to ruthenium(IV) hydrido(alkoxo) derivatives

The complexes [Cp*RuCl((i)Pr(2)PSX)] (X = pyridyl, quinolyl) react directly with alcohols ROH (R = Me, Et, (i)Pr, (n)Pr) and NaBPh(4), affording the novel cationic hydrido(alkoxo) derivatives [Cp*RuH(OR)((i)Pr(2)PSX)][BPh(4)]. These ruthenium(IV) compounds result from the formal oxidative addition of the alcohol to the 16-electron fragment {[Cp*Ru((i)Pr(2)PSX)](+)}, generated in situ upon chloride dissociation. The hydrido(alkoxo) complexes are reversibly deprotonated by a strong base such as KOBu(t), yielding the neutral alkoxides [Cp*Ru(OR)((i)Pr(2)PSX)], which are remarkably stable toward β elimination and do not generate the corresponding hydrides. The hydrido(alkoxo) complexes undergo a slow electron-transfer process, releasing H(2) and generating the dinuclear ruthenium(III) complex [{Cp*Ru(κ(2)-N,S-μ S-SC(5)H(4)N)}(2)][BPh(4)](2). In this species, the Ru-Ru separation is very short and consistent with what is expected for a Ru≡Ru triple bond.     

Si-H activation of hydrosilanes leading to hydrido silyl and bis(silyl) nickel complexes

A general route for the synthesis of novel NHC stabilized nickel bis(silyl) and nickel hydrido silyl complexes is presented. The reaction of [Ni(2)((i)Pr(2)Im)(4)(COD)] 1 ((i)Pr(2)Im = 1,3-di-isopropyl-imidazolin-2-ylidene) with hydrosilanes H(n)SiR(4-n) leads to complexes of the type [Ni((i)Pr(2)Im)(2)(SiH(n-1)R(4-n))(H)] or [Ni((i)Pr(2)Im)(2)(SiH(n-1)R(4-n))(2)].     

Reactions of a hydrido(hydrosilylene)tungsten complex with oxiranes

Reactivity of a hydrido(hydrosilylene)tungsten complex, Cp¹(CO)₂(H)WSi(H)[C(SiMe₃)₃] (1), toward oxiranes was investigated. Treatment of 1 with racemic mono-substituted oxiranes with a substituent R (R = Ph, vinyl, ^tBu, or ⁿBu) at room temperature produced dihydrido(vinyloxysilyl)tungsten complexes, (E)- and/or (Z)-Cp¹(CO)₂(H)₂W{Si(H)(OCHCHR)[C(SiMe₃)₃]} [(E/Z)-2: R = Ph, (E)-3: R = vinyl, (E)-4: R = ^tBu, (E/Z)-5: R = ⁿBu] in high yields via regioselective ring-opening of oxiranes. When the substituent R on oxirane was relatively large, (E)-isomers (2, 3, and 4) were obtained predominantly (87–97%), while the substituent was a relatively small ⁿBu group, an approximately 1:1 mixture of (E)- and (Z)-isomers [(E/Z)-5] was obtained. Reaction of 1 with 2,2-dimethyloxirane afforded the corresponding complex, Cp¹(CO)₂(H)₂W{Si(H)(OCHCMe₂)[C(SiMe₃)₃]} (6), quantitatively. A reaction mechanism is also discussed.     

A diastereoselective route to (±)-isoretronecanol

N-Unsubstituted imides react with 1-carboethoxycyclopropyltriphenylphosphonium tetrafluoroborate to yield N-acyl-Δ²-pyrroline, pyrrolizidine, and indolizidine derivatives.     

Simple route to ferrocenyl(alkyl)imidazoles

A suitable method for the synthesis of ferrocenyl(alkyl)imidazoles is proposed. The treatment of α-ferrocenylcarbinols with N,N′-carbonyldiimidazole affords the title compounds, are in more than 80% yields.