Brønsted Acid-Promoted Intramolecular Carbocyclization of Alkynals Leading to Cyclic Enones
摘要:
TFA-promoted exo carbocyclizations of nonterminal 7-alkynals gave good to excellent yields of seven-membered cycloalkenones, a medium-sized functionalized ring present in natural products with relevant pharmacological properties. Nonterminal 5- and 6-alkynals also gave very good yields of the corresponding exo cyclopentenones and cyclohexenones. On the other hand, terminal 5-alkynals gave endo carbocyclizations to cyclohexenones. These carbocyclizations can be considered as tandem alkyne hydration/aldol condensation processes.
Hydroalkylation of Alkynyl Ethers via a Gold(I)-Catalyzed 1,5-Hydride Shift/Cyclization Sequence
作者:Igor Dias Jurberg、Yann Odabachian、Fabien Gagosz
DOI:10.1021/ja9100134
日期:2010.3.17
A series of alkynyl ethers react with an electrophilic gold(I) catalyst to produce a range of structurally complex spiro or fused dihydrofurans and dihydropyrans via a 1,5-hydride shift/cyclization sequence. This hydroalkylation process, which is performed under practical experimental conditions, can be applied to terminal as well as ester-substituted alkynes. It allows the efficient conversion of
一系列炔基醚与亲电子金 (I) 催化剂反应,通过 1,5-氢化物转移/环化序列产生一系列结构复杂的螺或稠合二氢呋喃和二氢吡喃。这种在实际实验条件下进行的加氢烷基化过程可应用于末端和酯取代的炔烃。它允许通过将乙烯基金物质亲核加成到氧鎓中间体上,将二级或三级 sp(3) CH 键有效转化为新的 CC 键。形成新的五元或六元环的环异构化过程的立体选择性似乎取决于空间因素和炔烃取代模式。
Efficient Generation and Increased Reactivity in Cationic Gold via Brønsted Acid or Lewis Acid Assisted Activation of an Imidogold Precatalyst
作者:Junbin Han、Naoto Shimizu、Zhichao Lu、Hideki Amii、Gerald B. Hammond、Bo Xu
DOI:10.1021/ol501443m
日期:2014.7.3
Brønsted or Lewis acid assisted activation of an imidogold precatalyst (L-Au-Pht, Pht = phthalimide) offers a superior way to generate cationic gold compared with the commonly used silver-based system. It is also broadly applicable for most common gold-catalyzed reactions. For reactions that require milder conditions, milder acids can be used for optimized efficiency.