silylgrupper

Silyl groups are silicon-containing substituents used mainly as protecting groups for hydroxyl functionalities in organic synthesis. When attached to an alcohol, a silyl group forms a silyl ether that can withstand many reaction conditions, allowing multi-step sequences without affecting the protected site. The installation typically involves a silyl chloride or silyl triflate in the presence of a base such as imidazole or pyridine. Fluoride- or acid-mediated deprotection then regenerates the free alcohol.

Common silyl groups include trimethylsilyl (TMS), triethylsilyl (TES), tert-butyldimethylsilyl (TBS or TBDMS), triisopropylsilyl (TIPS), and tert-butyldiphenylsilyl (TBDPS). They vary in steric bulk and electronic properties, which translates into different stability under acidic, basic, or oxidative conditions. TMS is relatively labile; TBS/TBDMS and especially TBDPS are more robust; TIPS is intermediate with moderate steric hindrance.

Deprotection is commonly achieved with fluoride sources such as tetrabutylammonium fluoride (TBAF), HF-pyridine, or cesium fluoride in polar aprotic solvents; acidic conditions can also remove some silyl ethers, particularly the more labile ones. Selectivity can be used to deprotect individual hydroxyl groups in polyols, enabling iterative protection and deprotection schemes.

Beyond protecting alcohols, silyl groups also appear as reactive intermediates in silylation reactions and as components of silyl enol ethers in carbonyl chemistry. Their wide adoption stems from simple installation, tunable stability, and straightforward removal under mild conditions.