The oxidation of the carbon-silicon bond

A phenyldimethylsilyl group attached to carbon can be converted into a hydroxy group 1→5, with retention of configuration at the migrating carbon, by any of three main methods. The first involves protodesilylation, to remove the phenyl ring from the silicon atom, followed by oxidation of the resulting functionalised silicon atom using peracid or hydrogen peroxide. The second uses mercuric acetate for the same purpose, and can be combined in one pot with the oxidative step using peracetic acid. This method has a variant in which the mercuric ion is combined with palladium(II) acetate, both in less than stoichiometric amounts. The third uses bromine, which can also be used in one pot in conjunction with peracetic acid. In this method, but not in the method based on mercuric acetate, the peracetic acid may be buffered with sodium acetate. The method using bromine as the electrophile for removing the benzene ring has a more agreeable variant in which it is administered in the form of potassium bromide, which is oxidised to bromine by the peracetic acid. The scope and limitations of each of these methods are reported with a range of examples possessing between them many of the common functional groups. Simple benzene rings, alcohols, ethers, esters, amides and nitriles are compatible with all three methods, and ketones do not undergo Baeyer–Villiger reaction under any of the conditions. Amines, however, are oxidised to amine oxides. Ketones may be brominated in the third of the three main recipes. The absence of acid in the third method makes it especially valuable when the phenyldimethylsilyl group has a neighbouring nucleofugal group such as hydroxy or acetoxy. Carbon–carbon double bonds are incompatible with the methods, except for terminal monosubstituted double bonds, which can survive the conditions used in the first of the three methods.

The phenyldimethylsilyl group as a masked hydroxy group

The relative stabilities of the R2XO, trans-RXOR, and cis-RXOR isomers (X = C, Si, Ge, Sn, Pb; R = H, CH3) were investigated by ab initio and DFT pseudopotential calculations. Geometry optimizations and frequency computations were performed at the MP2 and Becke3LYP levels with DZ+P basis sets. MP4SDTQ/(DZ+P)//MP2/DZ+P and CCSD(T)/(DZ+P)//MP2/DZ+P single point calculations gave high level ab initio data. The CCSD(T)/(DZ+P)//MP2/(DZ+P) and the Becke3LYP/(DZ+P) relative energies both agree and show that the C2v H2XO isomers (with the exception of formaldehyde) are the least stable and that the cis- and trans-HXOH Cs isomers are very close in energy. Acetone and dimethylsilanone are the most stable isomers in the Me2XO series. However, with the notable exception of HPbOH, the H2XO compounds are not stable thermodynamically toward cyclotrimerization or to hydration. The NPA/NLMO charges, bond orders, and orbital hybridizations support the polar description -O:::X+R2 of all metal “double bond” species. The -O::...

H2XO and (CH3)2XO Compounds (X = C, Si, Ge, Sn, Pb): Double Bonds vs Carbene-Like StructuresCan the Metal Compounds Exist at All?

Tetrahedron report number 234 Synthetic aspects of the use of organosilicon compounds under nucleophilic catalysis conditions

Chemoselectivity of organometallic reactions : A hsab appraisal

The siliconoxygen double-bonded intermediates

Reactions of compounds containing SnLi and GeLi bonds with organic and organometallic peroxides

Kinetics of the catalytic rearrangement of organosilicon peroxides

Study of the mechanism of the catalytic rearrangement of triphenyl(triphenylsilylperoxy)germane

New rearrangement of triphenyl(triphenylsilylperoxy)germane catalyzed by nucleophiles

V.A. Yablokov

Papers

The siliconoxygen double-bonded intermediates

Reactions of compounds containing SnLi and GeLi bonds with organic and organometallic peroxides

Kinetics of the catalytic rearrangement of organosilicon peroxides

Study of the mechanism of the catalytic rearrangement of triphenyl(triphenylsilylperoxy)germane

New rearrangement of triphenyl(triphenylsilylperoxy)germane catalyzed by nucleophiles