Transcription of Protecting Groups Handout A
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Chem 6352 Protecting GroupsHydroxyl ProtectionMethyl EthersFormation:Stability: :Methyl ethers, with the exception of aryl methyl ethers, are often difficult to remove. However, there are , EtSH PhSe-Ph2P-Me3 SiIStable to Acid and BaseCH2N2, SiO2 or HBF4 NaH, MeI, THFM ethylthiomethyl Ethers (MTM)Formation:Stability:Cleavage:MeSCH2 Cl, NaH, THFS table to base and mild acidHgCl2, CH3CN, H2 OAgNO3, THF, H2O, baseOHOMeOOOMeOBzAlBr3, EtSHOOOHOBzTL 1987, 28, :TheMTMgroupisanicesubstitutedmethylethe rprotecting group that can be removed under neutral conditions employing the indicated of 1,2- and 1,3-diolsTrityl EthersFormation:Stability: :The trityl group usually goes on and comes off easily.
diols. It forms readily and is easily removed. Generally, the acetonide will form a dioxolane selectively over a dioxane. Ph Ph Ph Theprotectinggroupsthatmask1,2-and1,3-diols(formingeitherthe dioxolane or dioxane, respectively) are often referred to (PREFIX)ylidenes, where the prefix depends on the nature of R and R 1. OO OO RR1 RR 1 dioxolane ...
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