Tetrahydrofuranyl ethers

Ph2CHC02-2-tetrahydrofuranyl, 1% TsOH, CCI4, 20°, 30 min, 90-99% yield. The authors report that formation of the THF ether by reaction with 2-chlorotetrahydrofuran avoids a laborious proce ure that is required when dihydrofuran is used. In addition, the use of dihydrofuran to protect the 2 -OH of a nucleotide gives low yields (24-42%)." The tetrahydrofuranyl ester is reported to be a readily available, stable solid. A tetrahydrofuranyl ether can be cleaved in the presence of a THP ether. ... 

Although alcohols are oxidized by tetra-n-butylammonium persulphate when the reaction is conducted in dichloromethane, tetrahydropyranyl ethers have been produced (>90%) when attempts to oxidize the alcohol are conducted in tetrahydro-pyran (see Chapter 10) [ 19], Tetrahydrofuranyl ethers have been prepared by an analogous method [20,21 ]. Base-mediated elimination of halo acids from P-halo alcohols under phase-transfer catalysed conditions produce oxiranes in high yield (70-85%). The reaction has particular use in the synthesis of epihalohydrins from p,y-dihalo alcohols [22],... 

Tetrahydropyranyl (TUP) and tetrahydrofuranyl ethers are important protecting groups for alcohols and phenols in organic synthesis, but they can also be converted to other useful functional groups [8, 118]. For example, allylation of a TUP ether should yield a highly functionalized molecule (Scheme 15). 

Reaction of primary or secondary alcohols (72) with BrCCl3 and tetrahydrofuran leads to the generation of 2-tetrahydrofuranyl ethers (73) in good yields. The reaction comprises of the abstraction of an a-hydrogen atom of THF by CC13, subsequent reaction of the tetrahydrofuranyl radical with BrCCl3, and the polar reaction of the formed a-bromotetrahydrofuran with alcohol to form 2-tetrahydrofuranyl ether, as shown in eq. 2.35 [79]. 

Cyclic ethers are oxidized to lactones in the presence of cerium(IV) salts. Treatment of tetrahydiofu-ran with cerium(rV) ammonium nitrate in the presence of primary, secondary or tertiary alcdiols leads to the formation of the corresponding tetrahydrofuranyl ethers in quantitative yield. Fuitfaermoie, 4-meth-oxybenzyl ether derivatives of carbohytbates are selectively deprotected to the parent alcohols on reaction with cerium(IV) ammonium nitrate in aqueous acetonitrile. ... 

Table 4 Reductive Cleavage of Tetrahydrofuranyl Ethers with H2AIC] in Ether at Room Temperature...

The reactions of ozone with simple tetrahydropyranyl ethers and conforma-tionally rigid p-glycosides were indeed discovered to give the corresponding hydroxy Z-esters exclusively under kinetically controlled conditions lactone formation was not observed [8-10]. For instance, p-D-glucopyranoside 131 reacted under acetylating conditions to form 132 exclusively, Eq. 33. The reactions of the tetrahydrofuranyl ethers 133, Eq. 34, and 135, Eq. 36, were similar to that of 131 only the esters 134 and 136 were obtained, respectively. 

Scheme 22. Formation of tetrahydrofuranyl ethers under mild radical conditions...

Tetrahydrofuranyl ethers. Formation of such ethers (81-97%) from alcohols in refluxing THF is the result of radical coupling. 

Tetrahydrofuranyl ethers (4) are also smoothly oxidized to 7-hydroxy esters... 

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