Dimesityl

Also related is the synthesis of 2,2-dimesityl-l-(2,4,6-triisopropylphenyl)g-ermaphosphene by the reaction between difluorodimesitylgermane and the appropriate dilithiophosphide.35... 

The success of this transformation depends upon the oxidation potential of the ESE group (Eox 1.5 V), which is lower than that of the alkyl silyl ether group (Eax 2.5 V). Recently, Schmittel et al.35 showed (by product studies) that the enol derivatives of sterically hindered ketones (e.g., 2,2-dimesityl-1-phenyletha-none) can indeed be readily oxidized to the corresponding cation radicals, radicals and a-carbonyl cations either chemically with standard one-electron oxidants (such as tris(/>-bromophenyl)aminium hexachloroantimonate or ceric ammonium nitrate) or electrochemically (equation 10). 

These authors also noted that the electron-donor ability of various derivatives of 2,2-dimesityl-1-phenylethenol decreases in the order enolate > enol > enol silyl ether > enol phosphate > enol acetate. As such, a simple derivatization allows the ready modulation of the electron-donor properties of ends. 

Several polysilabicyclosilirenes (79) have been obtained in the reactions of polysil-acyclooctynes (78) with dimesitylsilylene generated from the photolysis of 2,2-dimesityl-l,l,l,3,3,3-hexamethyltrisilane (Eq. 8). Thermolysis of bis(silacyclo-propane) (80) in the presence of bis(trimethylsilyl)acetylene at 60 °C affords bis-(silacyclopropene) (81) in 61% yield (Scheme 14.41). ... 

On the other hand, an intramolecular reversible rotation of the two mesityl rings in 2,2-dimesityl-l-(trimethylsilyl)ethenol (202) occurs to give 203 (equation 83)258. The free energy of activation for the rotation (AG ) leading to the enantiomerization is... 

FIGURE 1. Representative cyclic voltammogram of a 2,2-dimesityl enol in which the two electron removals involved in the ECE determining steps proceed at the same potential value . Reproduced from Reference 134 by permission of Wiley-VCH... 

TABLE 1. Formal electrode potentials (vs. SCE) for the enol-centred oxidations exhibited by the 2,2-dimesityl enols (77) and their derived benzofutans (78)... 

As silicon is the element most similar to carbon, compounds containing multiple bonds to Si have long been sought. Tetramesityldisilene, the first stable compound containing a silicon-silicon double bond, was initially prepared in 1981 by ultraviolet irradiation of 2,2-dimesityl-l,l,l,3,3,3-hexamethyltrisilane. Photolysis of the trisilane produces dimesitylsilylene, which dimerizes to form the disilene. 

Synthesis of AU Iidene 1,2-Oxasiletanes. The regiospecific oxidation of siliranes to 1,2-oxasiletanes can be accomplished in moderate yield with diphenyl sulfoxide. When 1,1-dimesityl-2Z-neopentylidenesilirane was heated with diphenyl sulfoxide in benzene, 2,2-dimesityl-4Z-neopentylidene-l,2-oxasiletane was formed in 70% yield (eq 11). In contrast, use of cyclo-hexyldimethylamine A-oxide instead of diphenyl sulfoxide gave the isomeric 1,2-oxasiletane in 44% yield along with mesitol in 40% yield (eq 12). 

Escendie, 1., Courte, C., Stage, J., Andrianarison, M., and Andrinizake, 1. D. (1985). 2,2,-Dimesityl-l-(2,4,6-tri-tert-butyl phenyl) germa-phosphene The first stable compound with a germanium-phosphorus double bond, Am. Chem. Soc. 107,3378. 

---