An Alkyne Diboration/6π-Electrocyclization Strategy for the Synthesis of Pyridine Boronic Acid Derivatives
作者:Helena Mora-Radó、Laurent Bialy、Werngard Czechtizky、María Méndez、Joseph P. A. Harrity
DOI:10.1002/anie.201601084
日期:2016.5.4
A new and efficient synthesis of pyridine‐based heteroaromatic boronic acid derivatives is reported through a novel diboration/6π‐electrocyclization strategy. This method delivers a range of functionalized heterocycles from readily available startingmaterials.
Tertiary Amine Mediated Tandem Cross-Rauhut-Currier/Acetalization Reactions: Access to Functionalized Spiro-3,4-Dihydropyrans
作者:Weijun Yao、Yihua Wu、Gang Wang、Yiping Zhang、Cheng Ma
DOI:10.1002/anie.200905091
日期:2009.12.14
γ‐Proton transfer furnished the highly selective title reaction in which cyclic β‐haloenals 1 react with β,γ‐unsaturated α‐ketoesters 2 to generate functionalized spiro‐3,4‐dihydro‐2H‐pyrans 3 having an α‐quaternary carbon center and an adjacent vinyl halide group in skeleton. DBU=1,8‐diazabicyclo[5.4.0]undec‐7‐ene, Tos=4‐toluenesulfonyl.
Gold-Catalyzed Cyclization-Cycloaddition Cascade Reactions of Allenyl Acetals with Nitrones
作者:Dhananjayan Vasu、Rai-Shung Liu
DOI:10.1002/chem.201201777
日期:2012.10.22
Gold and silver: When allenyl acetals and nitrones are treated with a catalytic amount of a gold complex and a silver salt they react through a cyclization—cycloaddition cascadereaction to give a mixture of diastereomeric tricyclic products. The mixture converges to a single product upon acid hydrolysis (see scheme). The key intermediate is postulated to be a 1‐methoxyfulvene species.
Functionalized Alkenylzinc Reagents Bearing Carbonyl Groups: Preparation by Direct Metal Insertion and Reaction with Electrophiles
作者:Christoph Sämann、Matthias A. Schade、Shigeyuki Yamada、Paul Knochel
DOI:10.1002/anie.201302058
日期:2013.9.2
cyclic and acyclic alkenylzinc reagents bearing functional groups such as aldehyde, keto, and ester groups were readily prepared by either direct zinc insertion in the presence of LiCl or by magnesiuminsertion in the presence of LiCl and ZnCl2. Subsequent functionalization reactions, such as Negishi cross‐couplings, acylations, and allylations, furnished polyfunctional compounds in excellent yields
(254 nm) smoothly yielded hexahydrofluorenones and related structures. This photo‐Nazarov reaction could also be applicable to the substrates carrying β‐alkyl groups on the enone, which gave corresponding polycyclic rings containing quaternary centers. These photo‐electrocyclized products may prove useful for synthesizing a variety of natural products and their derivatives. Further application of this