Reaction of the acetals with TESOTf-base combination; Speculation of the intermediates and efficient mixed acetal formation

被引:108
作者
Fujioka, H [1 ]
Okitsu, T [1 ]
Sawama, Y [1 ]
Murata, N [1 ]
Li, R [1 ]
Kita, Y [1 ]
机构
[1] Osaka Univ, Grad Sch Pharmaceut Sci, Suita, Osaka 5650871, Japan
关键词
D O I
10.1021/ja060328d
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We report here unexpected highly chemoselective deprotection of the acetals from aldehydes. Treatment of acetal compounds from aldehydes with TESOTf-2,6-lutidine or TESOTf-2,4,6-collidine in CH2Cl2 at 0 degrees C followed by H2O workup at the same temperature caused the conversion of the acetal functions to aldehyde functions. The reaction had generality and was applied to many acetal compounds. Study using various bases revealed the reaction and reached the best combination of TESOTf-base. It was very mild and highly chemoselective and proceeded under weakly basic conditions. Then, many functional groups such as allyl alcohol, silyl ether, acetate, methyl ether, triphenylmethyl (Tr) ether, 1,3-dithiolane, methyl ester, and tert-butyl ester could survive under these conditions. Furthermore, this methodology could selectively deprotect the acetals in the presence of ketals as the most characteristic feature, although this chemoselectivity is difficult to achieve by other previously reported methods. A detailed study of the reaction including MS and NMR studies revealed the reaction mechanism for determining the structures of the intermediates, pyridinium-type salts. These intermediates had a weak electrophilicity and were successfully applied to the efficient formation of the mixed acetals in high yields.
引用
收藏
页码:5930 / 5938
页数:9
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