β-halo α,β-unsaturated aldehydes by a microwave-assisted Knoevenagel reaction. The β-halo-α,β-unsaturated aldehydes were, in turn, efficiently synthesized from the corresponding ketones by a Vilsmeier formylation reaction. The protocol was used to synthesize several novel steroidal and nonsteroidal fused 2-aminopyridine derivatives. 2-Aminopyridines were synthesized from β-halo α,β-unsaturated aldehydes
An N-heterocyclic-carbene-catalyzed asymmetric formal [3+2] annulation reaction of isatin N-Boc ketimines (Boc = tert-butyloxycarbonyl) and 3-bromoenals was developed for the construction of spiro[indoline-3,2′-pyrrole] derivatives with one quaternary chiral center in good yields (up to 81 % yield) with excellent enantioselectivity (up to 99 % ee).
Chiral Spirooxindole–Butenolide Synthesis through Asymmetric N-Heterocyclic Carbene-Catalyzed Formal (3 + 2) Annulation of 3-Bromoenals and Isatins
作者:Chenguang Zheng、Weijun Yao、Yucheng Zhang、Cheng Ma
DOI:10.1021/ol502365r
日期:2014.10.3
By using an N-heterocyclic carbene catalyst bearing a hydroxyl moiety, the asymmetric formal (3 + 2) cyclization of aryl 3-bromoenals and isatins was achieved to produce a series of chiral spirooxindole–butenolides including an alkenyl-substituted compound, which underwent benzannulations with benzynes to form intriguing spirocyclic scaffolds.
Construction of [2,5]-Furanophanes by Carbene-Mediated Alkynyl Migration Cyclization
作者:Qiu Shi、Yang Chen、Tongxiang Cao、Shifa Zhu
DOI:10.1021/acs.orglett.2c03185
日期:2022.11.11
Heterophanes are widely found in natural products and drug molecules. Herein, an efficient method for the construction of [2,5]-furanophanes with differentring types and ringsizes was developed. This method is carried out with furan-free precursor throughintramolecular carbene-mediated alkynyl migration and tandem cyclization strategy. In addition, a series of tetrafuran structures can be obtained by oxidative
An efficient cobalt-catalyzed tandemone-pot method has been developed for the synthesis of polysubstituted imidazo[1,5-a]-N-heteroaromatics. The method involves Knoevenagel condensation followed by cobalt-catalyzed direct alkenylation to give the desired polysubstituted imidazo[1,5-a]pyridines and imidazo[1,5-a]isoquinolines in a one-pot manner. This method exhibits a broad substrate scope, provides
开发了一种高效的钴催化串联一锅法合成多取代的咪唑并[1,5 - a ]-N-杂芳烃。该方法涉及 Knoevenagel 缩合,然后是钴催化的直接烯基化,以一锅方式得到所需的多取代咪唑并[1,5- a ]吡啶和咪唑并[1,5 - a ]异喹啉。这种方法表现出广泛的底物范围,提供中等至良好(39-74%)的产量,并且可以放大到克级。