Synthetic Developments in Unsymmetrical Silyl Ketal Synthesis

The development of synthetic methods is a very important branch of natural product synthesis, and complex target-oriented synthesis. The new chemical methods that are developed by chemists simplify the process of synthesis. This simplification generally leads to a shorter number of steps in the synthesis and therefore a more efficient synthesis. New synthetic methods are usually developed with simple substrates which highlight the main functional group transformation. These methods can be difficult to be transferred to a more complex molecule therefore, it is important that a new synthetic method demonstrates the scope and limitation of the method. 

Synthetic methods using organosilanes are vital to organic synthesis. Formation of silyl ethers and silyl ketals are among the examples. There have been significant developments in silyl ether synthesis and applications to organic chemistry over the years. These compounds have proved to be versatile, safe, and compatible with a variety of reaction conditions. For these reasons silyl ethers and silyl ketals have been widely employed in organic synthesis. They are 

Silicon tethers based on bis-alkoxysilanes (silyl ketals) are commonly prepared from the dichlorosilanes by reaction with an alcohol in the presence of base. These conditions are not compatible with some base labile compounds. To make unsymmetrical bis-alkoxysilanes requires a method for breaking the symmetry of the dichlorosilane. Without such a method, one must accept a statistically determined mixture of mono-alkoxy and bis-alkoxy products. This may be acceptable for inexpensive readily available alcohols, but it precludes the use of bis-alkoxysilane tethers for high-value synthetic intermediates. To overcome these limitations to 

There have been several reports of catalytic methods for alcoholysis of trialkylsilanes,10-17 however only a few of these papers have included reactions with dialkyl(dihydrido)silanes.9a,d 15 Among the more reactive catalysts for the preparation of trialkylsilyl ethers from silyl hydrides 

There have been a few reports on the controlled catalytic alcoholysis of dialkylsilanes to produce the mono-hydrido silyl ether. 9a,c,15 16 One such report is by Corriu and Moreau who have illustrated the use of either (PPh3)3RJiCl, (PPh3)3RuCl or Raney Ni to execute the controlled alcoholysis of diphenylsilane to give the mono-functional alkoxysilane as the only product.93 Doyle attempted to use the Rh2(pfb)4 catalyst with diphenylsilane and trans- 1,2-cyclohexanediol to prepare the cyclic silyl ketal,16 but this was not successful, perhaps because the trans-fused 

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Synthetic Developments in Unsymmetrical Silyl Ketal Synthesis 2.1. Introduction... 

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