117658-01-2Relevant academic research and scientific papers
Regioselective Preparation of 2,4-, 3,4-, and 2,3,4-Substituted Furan Rings. 2. Regioselective Lithiation of 2-Silylated-3-substituted Furan Rings
Bures, Edward,Nieman, James A.,Yu, Shuyuan,Spinazzé, Patrick G.,Bontront, Jean-Louis J.,Hunt, Ian R.,Rauk, Arvi,Keay, Brian A.
, p. 8750 - 8759 (1997)
A new method for the preparation of 3,4- and 2,5-disubstituted furan rings is described. A variety of 2-silylated-3-(hydroxymethyl)furans and 2-silylated-3-furoic acids lithiate exclusively at C-4 when treated with 2.2 equivs of BuLi. The resulting dianions were quenched with a variety of electrophiles to provide 2-silylated-3-(hydroxymethyl)-4-substituted furans and 2-silylated-4-substituted 3-furoic acids in good to excellent yields. Removal of the silyl group (n-Bu4NF) provided a variety of 4-substituted-3-(hydroxymethyl)furans and methyl 4-substituted-3-furoates, respectively. The latter esters were prepared due to difficulties encountered in isolating 4-substituted-3-furoic acids. The site of lithiation was altered by protecting the 3-hydroxyl group with a triethylsilane. Lithiation of 2-silylated-3-(((triethylsilyl)oxy)methyl)furan with 1.2 equivs of BuLi followed by the addition of electrophiles provided 2-silylated-3-(((triethylsilyl)oxy)methyl)-5-substituted furan rings. Subsequent removal of both silyl groups provided 2,4-disubstituted furan rings in moderate to good yields. A rationale is provided to explain why protection of the hydroxyl group at C-3 leads to a change in lithiation from the C-4 to the C-5 position of the furan ring. In addition, an explanation for the observed effect of adding HMPA or LiCl to the solution during the lithiation of 2-(tert-butyldimethylsilyl)-3-(hydroxymethyl)furan is provided.
THE REGIOSPECIFIC FORMATION AND REACTIONS OF 4-LITHIO-2-(t-BUTYLDIMETHYLSILYL)-3-(HYDROXYMETHYL)FURAN: AN APPROACH TO 3,4-DISUBSTITUTED FURANS
Bures, J. Edward,Keay, A. Brian
, p. 1247 - 1250 (1988)
4-Lithio-2-(t-butyldimethylsilyl)-3-(hydroxymethyl)furan, generated by treating 2-(t-butyldimethylsilyl)-3-(hydroxymethyl)furan 2 with 2.2 equivalents of n-butyllithium (DME/0 deg C/15 min), is trapped by a variety of electrophiles to produce, after desilylation, 3,4-disubstituted furans in good to moderate yields.
