Scope and Limitations of the Photooxidations of 2-(α-Hydroxyalkyl)furans: Synthesis of 2-Hydroxy-exo-brevicomin
摘要:
Photooxygenation of 2-(alpha-hydroxyalkyl)furans at 5 degrees C in MeOH followed by in situ reduction affords, in one synthetic operation, 6-hydroxy-3(2H)-pyranones and/or 5-hydroxy-2(5H)-furanones. The relative ratio of the final products is highly dependent on the substitution of the starting furan substrate. Photooxygenation of 2-(alpha,beta-dihydroxyalkyl)furans followed by in situ reduction and ketalization with acid rapidly provides the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework. This new methodology was successfully applied to the synthesis of 2-hydroxy-exo-brevicomin.
Palladium(II)-Catalyzed Efficient C-3 Functionalization of Indoles with Benzylic and Allylic Alcohols under Co-Catalyst, Acid, Base, Additive and External Ligand-Free Conditions
作者:Debjit Das、Sujit Roy
DOI:10.1002/adsc.201300048
日期:2013.5.3
The bis(acetonitrile)palladium(II) chloride complex, PdCl2(MeCN)2, efficiently catalyzes the regioselective alkylation of indoles with various benzylic and allylicalcohols under moisture and air insensitive conditions. Notably the reaction does not require any other co‐catalyst, acid, base, additive, or external ligand.
catalytic methods for the oxidative furan-recyclizations remain scarcely investigated. Given this, we report a means of manganese-catalyzed oxidations of furan with low loading, achieving the Achmatowiczrearrangement in the presence of hydrogen peroxide as an environmentally benign oxidant under mild conditions with wide functional group compatibility.
Iridium-Catalyzed Dynamic Kinetic Isomerization: Expedient Synthesis of Carbohydrates from Achmatowicz Rearrangement Products
作者:Hao-Yuan Wang、Ka Yang、Scott R. Bennett、Sheng-rong Guo、Weiping Tang
DOI:10.1002/anie.201503151
日期:2015.7.20
A highly stereoselective dynamickineticisomerization of Achmatowiczrearrangementproducts was discovered. This new internal redox isomerization provided ready access to key intermediates for the enantio‐ and diastereoselective synthesis of a series of naturally occurring sugars. The nature of the de novo synthesis also enables the preparation of both enantiomers.
Lipase B from Candida antarctica catalyzes the oxidative ring expansion of furfuryl alcohols using aqueous hydrogen peroxide to yield functionalized pyranones under mild conditions. The method further allows for the preparation of corresponding piperidinone derivatives by enzymatic rearrangement of N-protected furfurylamines.
来自南极念珠菌的脂肪酶 B 使用过氧化氢水溶液催化糠醇的氧化扩环,在温和条件下产生官能化的吡喃酮。该方法还允许通过N-保护的糠胺的酶促重排来制备相应的哌啶酮衍生物。
Alcohol dehydrogenases can act as powerful catalysts in the preparation of opticallypure γ-hydroxy-δ-lactones by means of an enantioconvergent dynamic redox isomerization of readily available Achmatowicz-type pyranones. Imitating the traditionally metal-mediated "borrowing hydrogen" approach to shuffle hydrides across molecular architectures and interconvert functional groups, this chemoinspired and