Carbonyl compounds 1 were converted to the corresponding 1,3-dioxolanes 2 and 1,3-dioxanes 4 with ethylene glycol and 2,2-dimethyl-1,3-propandiol, respectively, in the presence of 1-3 mol% of N-(benzyl, 4-methylbenzyl or 4-methoxybenzyl)-2(or -4)-cyanopyridinium hexafluoroantimonates 3. The catalyst 3d was also effective for the tetrahydropyranylation.
3,3,9,9-Tetramethyl-1,5,7,11-tetraoxaspiro[5.5]undecane is introduced as a new, stable and chemoselective reagent for the protection of aldehydes and ketones under mild reaction condition in high yield.
Low-Valent Titanium Mediated Reductive Cleavage of Benzylidene Acetals: A Modified Mcmurry Reaction
作者:Sanjay Talukdar、Sandip K. Nayak、Asoke Banerji
DOI:10.1080/00397919808004285
日期:1998.7
Abstract Reductive cleavage of benzylideneacetals using low-valent titanium reagent results in the formation of aryl alkanes and stilbenes. Aliphatic acetals, however, remain unaffected. This cleavage offers an attractive, alternate stereoselective route to stilbenes in a modified McMurry reaction.
Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups
作者:Brian T. Gregg、Kathryn C. Golden、John F. Quinn
DOI:10.1016/j.tet.2008.01.118
日期:2008.4
Aldehydes and ketones, including acetophenone and benzophenone, are readily protected under mild, neutral conditions in the presence of various alcohols or orthoformates and catalytic amounts of indium(III) trifluoromethanesulfonate (<0.8 mol %) under either room temperature or mild heating conditions to give the corresponding cyclic and acyclic acetals and ketals in good to excellent yields. Acid sensitive functional groups, N-Boc, THP, and TBDMS do not undergo competitive deprotection under the reported conditions. (C) 2008 Elsevier Ltd. All rights reserved.
KANTLEHNER W.; GUTBROD H.-D., LIEBIGS ANN. CHEM., 1979, NO 9, 1362-1369