Allylation of Aldehydes Promoted by the Cerium(III) Chloride Heptahydrate/Sodium Iodide System: the Dependence of Regio- and Stereocontrol on the Reaction Conditions
The cerium(III) chloride heptahydrate/sodium iodide complex (CeCl3 ⋅ 7 H2O/NaI) acts as a useful promoter in the carbon-carbonbond forming reaction by addition of allyltributylstannanes to aldehydes. The reaction of 2-butenyltributylstannane shows that the regio- and the stereochemical outcomes depend on the reaction conditions. When the promoter is adsorbed on a solid support (aluminum oxide), a
铈(III)七水合氯化/碘化钠复合物(加入CeCl 3 ⋅7 H 2 O / NAI)作为在碳-碳键形成通过加入allyltributylstannanes醛的反应的有用的启动子。2-丁烯基三丁基锡烷的反应表明区域和立体化学结果取决于反应条件。当促进剂吸附在固体载体(氧化铝)上时,在无溶剂条件下会观察到非常普遍的γ加合物形成。相反,当反应在乙腈作为溶剂中进行时,α-加合物占优势。在最后一种情况下,观察到完全的立体控制,以高几何纯度获得较不稳定的(Z)-异构体。
A Novel Preparation of Allylic Trichlorotins from α,α-Diisopropylhomoallylic Alcohols and Its Application to Carbonyl Allylations
α,α-Diisopropylhomoallylic alcohols react with tin(II) chloride and NCS in CH2Cl2 at -40 °C to -60 °C to produce allylic tins and diisopropyl ketone, and the allylic tins in situ cause nucleophilic addition to aldehydes to afford α-substituted homoallylic alcohols.
diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does proceed with tin(II) iodide and exhibits gamma-syn selectivity which is unusual for a Barbier-type carbonylallylation. In the carbonylallylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of tetrabutylammoniumiodide (TBAI) accelerates
Tandem Allylboration-Prins Reaction for the Rapid Construction of Substituted Tetrahydropyrans: Application to the Total Synthesis of (−)-Clavosolide A
作者:Alba Millán、James R. Smith、Jack L.-Y. Chen、Varinder K. Aggarwal
DOI:10.1002/anie.201511140
日期:2016.2.12
Tetrahydropyrans are common motifs in natural products and have now been constructed with high stereocontrol through a three-component allylboration-Prins reaction sequence. This methodology has been applied to a concise (13 steps) and efficient (14 % overall yield) synthesis of the macrolide (-)-clavosolide A. The synthesis also features an early stage glycosidation reaction to introduce the xylose
Crotylboration of aldehydes with E- or Z-crotylboronates in the presence of catalytic amounts of indium triflate provides the corresponding 4-substituted homoallylic alcohols.