Dibutyltin oxide mediated diastereoselective cyclodehydration/sulfonylation of 1,2,4-triols
                                
                                    
                                        作者:Makhosazana P. Gamedze、Comfort M. Nkambule                                    
                                    
                                        DOI:10.1016/j.tetlet.2015.02.083
                                    
                                    
                                        日期:2015.4
                                    
                                    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.