Ah` ... If we want to protect the resulting alcohol group then we can use THP ??
Sure, a THP (tetrahydropyran) group would probably be okay, but it all depends on what you are protecting the group from
. THP can also be problematic because you produce a new stereocenter in your compound, and therefore you could produce a diastereomeric mixture which is difficult to work with.
Silyl groups are probably the most common form of alcohol protecting groups, with trimethylsilyl (TMS) being the simplest (as PLU wrote above). The most common one in modern synthetic chemistry is almost certainly the t
-butyldimethylsilyl (TBS or TBDMS) group. The latter is favored because of its stability towards mild treatment with aqueous acid. The TMS group will often fall off under even modestly acidic conditions (such as workup conditions for a Grignard reaction) while a TBS group will survive. Silyl groups are also favored because they can be selectively deprotected with sources of F-
, such as tetra-n
-butylammonium fluoride. The TMS group is certainly useful in many cases, but if you need your alcohol to stay protected for more than one or possibly two steps of your synthesis, you probably want to use a bulkier silyl group. However, the lability of TMS can be useful because you can kind of "skip" the deprotection step sometimes!
For those of you familiar with the THP group, you will note that it is usually cleaved by treatment with relatively mild aqueous acid. In my experience, THP is more stable towards mild acid than TMS.