Protection 2- ethoxymethyl chloride

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. 

Reaction of 3, 5 -di- -butylsilanediyl derivatives of nucleosides with 2-(tri-methylsilyl) ethoxymethyl chloride (Sem chloride) gives the 2 -0-Sem derivatives 189, from which the 0-silyl protection can be removed by HF in pyridine. There have been further reports of the enzymic galactosylation of nucleosides at 0-5 using P-galactosidases. ... 

For (313), he began with the intact nucleoside 5-ethoxymethyl-2 -deoxyuridine (307) [160], After protection of the 3 - and 5 -hydroxy groups with p-chlorobenzoyl chloride, the resulting diester (308) was converted into a separable mixture of (309) (major) and (310) (minor). Alkylation of (35) with crude (309) gave (311) together with small amounts of unreacted (35) and a product tentatively identified as (310). Cleavage of the p-chlorobenzoates with methanolic sodium methoxide with concomitant transesterification yielded (312), which was saponified and then treated with barium acetate to afford the barium salt of (313). 

The aforementioned l,4-bis(2-hydroxyhexafluoroisopropyl)cyclohexane has been combined with the 2-trifluorometylacrylic structure [290,305,307]. The fluorodiol was half-protected with an ethoxymethyl group and reacted with 2-trifluoromethylacryloyl chloride in the presence of triethylamine to afford 2-[4-(2,2,2-trifluoro-l-ethoxymethoxy-l-trifluoromethylethyl)cyclo-hexane]hexafluoroisopropyl 2-trifluoromethylacrylate. This heavily fluorinated acrylate was copolymerized with 2-methyladamanty 2-trifluoromethylacrylate by anionic initiation with potassium acetate/18-crown-6 [307] as described in the literature [303] (Fig. 90). The copolymer (made from a 1 1 feed) was unexpectedly transparent with OD157 of 1.6/pm. However, imaging of the copolymer resists was sluggish perhaps due to their low Tg. Radical copolymerization was also performed with norbornene derivatives [290,305]. 

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