Dibutyltin oxide mediated diastereoselective cyclodehydration/sulfonylation of 1,2,4-triols
摘要:
Dibutyltin oxide (Bu2SnO) mediated cyclodehydration or sulfonylation of 1,2,4-triols is predictably diastereoselective depending on the steric bulk of the substituents at C4. A larger difference (Delta A-value >1 kcal/mol) leads to the syn-1,2,4-triols favouring cyclodehydration (78-85%) to form 3-hydroxytetrahydrofurans, with the anti-1,2,4-triols favouring monosulfonylation (66-87%). Triols from symmetrical ketones preferentially undergo cyclodehydration in high yield (>75%) due to a gem-disubstituent effect. Thus, the 1,2,4-triols derived from simple cyclic ketones also favour cyclodehydration to form spirocyclic 3-hydroxytetrahydrofurans in 72-79% yields. (C) 2015 Elsevier Ltd. All rights reserved.
A simple method for assigning the absolute configuration of benzoate derivatives of 1, 2, 4-triols have been established using a differential CD exiton chirality method.
Vanadium‐Catalyzed Enantioselective Desymmetrization of
<i>meso</i>
Secondary Allylic Alcohols and Homoallylic Alcohols
作者:Zhi Li、Wei Zhang、Hisashi Yamamoto
DOI:10.1002/anie.200802523
日期:2008.9.15
Vanadium-catalyzed epoxidation has extended substrate scope. In addition to various bis-allylic alcohols, bis-homoallylic alcohols can also be desymmetrized using our Vanadium-Bis-hydroxamic acid complexes.