Alcoholysis with a Reverse Order Addition of the Alcohols

Entry Mono-alkoxy silane Alcohol Time (h) Silyl ketal % Isolated yield 

The mono-alkoxy product from 2-phenylethanol and diisopropylsilane (la) was used in the evaluation (Table 11). When la was treated with (+)-ethyl lactate using 10 % Pd/C as 

We have utilized three different catalytic systems however during this investigation we have not thoroughly studied their mechanisms. The Rh2(OAc)4 system performed as expected, but the 10 % Pd/C and the Mn(CO)sBr catalytic systems gave us results that presented a need to consider their mechanism. 

We propose that the carbonyl oxygen of the (+)-ethyl lactate acts as a Lewis base forming an intramolecular pentacoordinated organosilicon compound. Pentacoordination from a 

In the case where the silyl ketal is made up of the 2-phenylethanol and (+)-ethyl lactate (3a), the more basic oxygen would be the one on the 2-phenylethanol moiety. However protonation and eventually dissociation of this alcohol leads back to the starting silyl ether. Protonation could also occur on the oxygen of the (+)-ethyl lactate moiety. Once the (+)-ethyl lactate is protonated it could dissociate resulting in newly formed silyl ether. This newly formed silyl ether can react with the dissociated (+)-ethyl lactate, or it can go on to react with another 2-phenethyl ethanol which is present in a higher concentration than the dissociated (+)-ethyl 

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Table 11. Catalytic Alcoholysis with a Reverse Order Addition of the Alcohols.

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