Trimethylsilyl ethoxymethyl Chloride

The resulting SEM ethers are stable under a variety of conditions. Most SEM ethers are cleaved with a fluoride anion source (eqs 4 and although this fragmentation is generally 

A list of General Abbreviations appears on the front Endpapers 

SEM-Cl has also proven useful in carbohydrate synthesis where the resulting SEM ethers can be cleaved under less acidic conditions than those required for the cleavage of MOM and MEM ethers (eq 10).  

Reagent for the Protection of Acids. Carboxylic acids can be protected as SEM esters (eq 11). Cleavage of the SEM esters occurs with refluxing methanol or magnesium bromide (eq 12)  

The stability of SEM ethers has necessitated the development of a variety of other deprotection methods. SEM protective groups are stable to the acidic conditions used to hydrolyze THP, TBDMS, and MOM ethers (AcOH, H2O, THE, 45 °C), but can be removed under strongly acidic conditions with trifluoroacetic acid SEM, MTM, and MOM ethers are selectively cleaved in the presence of MEM, TBDMS, and benzyl ethers with magnesium 

---

Trimethylsilyl)ethoxymethyl chloride (SEMCl) [76513-69-4] M 166.7, b 57-59"/8mm, d 0.942, n 1.4350. Dissolve in pentane, dry (MgS04), evaporate and dist residual oil in a vac. Stabilise with lOppm of diisopropylamine. Store under N2in a sealed container in a refrigerator. [Lipshutz and Pegram Tetrahedron Lett 21 3343 I980. ... 

Finally, the carbamoyllithium 122 was prepared by tin-lithium transmetallation at —105 °C from the corresponding carbamoylstannane 121. This tin compound was prepared by addition of tri-n-butyltin lithium to an isocyanate followed by quenching with SEMC1 [2-(trimethylsilyl)ethoxymethyl chloride]. The functionalized intermediate 122 was acylated with the ester 123 to give the product 124 in a model study towards the synthesis of mycalamides (Scheme 33)115. 

The product from Step 1 (59 mmol) and Hunig s base (48 mmol) were dissolved in 75 ml CH2CI2, 2-(trimethylsilyl)ethoxymethyl chloride (70.8 mmol) added, and the mixture stirred 3.5 hours at 50 °C then 15 hours at ambient temperature. The mixture was poured into 200 ml NH4OAC solution, extracted with EtOAc, purified by flash chromatography using silica gel with hexane/EtOAc, 9 1, and 9.6 g product isolated. 

Primary, secondary and tertiary alcohols can be protected in good yield as their 2-(trimethylsil-yl)ethoxymethyl ethers (abbreviated SEM ethers) by reaction with 2-(trimethylsilyl)ethoxymethyl chloride (SEM-Cl) in dichloromethane in the presence of Pr 2NEt. The resultant ethers are stable to the conditions used to remove THP and TMS ethers (3 1 1 THF HOAc H20). Deprotection takes place on treatment with TBAF in THF at 45 °C. 

ALCOHOLS Allyltrimethylsilane. (1 5-Cyclooctadiene)bis(methyldiphenylphos-phine)iridium hexafluorophosphate. Guaiacylmethyl chloride. Levulinic acid. )3-(Trimethylsilyl)ethoxymethyl chloride. 2-(Tiimethylsilyl)ethyl chloroformate. 

Preparative Method involves reaction of triphenylphosphine with 2-(trimethylsilyl)ethoxymethyl chloride in benzene at gentle reflux for 18 h. Upon cooling, the resulting phosphonium salt can be recovered by filtration and purified by triturating with diethyl ether in 94% yield. ... 

Related Reagents. Benzyl Chloromethyl Sulfide r-Butyl Chloromethyl Ether 2-Chloroethyl Chloromethyl Ether Chloromethyl Methyl Ether Chloromethyl Methyl Sulfide (p-Methoxy-benzyloxy)methyl Chloride 2-Methoxyethoxymethyl Chloride 2-(Trimethylsilyl)ethoxymethyl Chloride. 

Related Reagents. 2-(Trimethylsilyl)ethoxycarbonylimidazole 2-(Trimethylsilyl)ethoxymethyl Chloride 2-(Trimethylsilyl)-ethyl Chloroformate. 

---