我们报告了未活化的1,6-二炔与N-溴代琥珀酰亚胺(NBS)的Pd催化卤代环化反应。这种方法可生产立体定义明确的二溴取代的二氢吡喃,四氢吡啶和3-亚甲基环己烯,并带有环外双键附件,且收率很高。发现铜盐是该反应中有用的路易斯酸。从机理上讲,提出了一种形式上的抗碳氢键合和溴化物自由基促进的Pd II -Pd III -Pd I -Pd II催化循环,参与了二溴取代产物的形成。将二氢吡喃衍生物进一步官能化后进行B(C 6 F 5)3-催化的开环并还原得到具有优异立体选择性的二溴代1,3-二烯。
Highly Enantioselective [2+2+2] Cycloaddition of Enediynes Enabled by Cobalt/Organophotoredox Cooperative Catalysis
作者:Takeshi Yasui、Rine Tatsumi、Yoshihiko Yamamoto
DOI:10.1021/acscatal.1c02410
日期:2021.8.6
Herein, we report dual cobalt and photoredox catalysis enabled [2+2+2] cycloaddition of enediynes to produce tricyclic cyclohexadienes bearing a quaternary bridgehead carbon. A variety of enediynes were used, and the corresponding cyclohexadienes were obtained in good to high yields. The use of a chiral ligand, (S)-Segphos, enabled a highly enantioselective reaction allowing access to highly enantio-enriched
在此,我们报告了双钴和光氧化还原催化使烯二炔的 [2+2+2] 环加成产生带有四元桥头碳的三环环己二烯。使用了多种烯二炔,并以良好到高产率获得了相应的环己二烯。手性配体 ( S )-Segphos 的使用可实现高度对映选择性反应,从而获得高度对映体富集的环己二烯。
Ruthenium-catalyzed Hydrocarbamoylative Cyclization of 1,6-Diynes with Formamides
The ruthenium-catalyzed hydrocarbamoylative cyclization of 1,6-diynes with formamides afforded exocyclic-diene-type α,β,γ,δ-unsaturated amides with 100% stereoselectivity. A plausible mechanism involving ruthenium hydride species is proposed to explain the experimental results. Some control experiments, performed using DMF-d7 and/or D2O, corroborate the proposed mechanism.
A Combined Transition-Metal-Catalyzed and Photopromoted Process: Synthesis of 2,3-Fused 4-Phenylnaphthalen-1-yl Carboxylates from 1,7-Diaryl-1,6-diynes
2,3‐Fused 4‐phenylnaphthalen‐1‐yl carboxylates were synthesized in a step‐ and atom‐economical manner using a ruthenium‐catalyzed hydrocarboxylative cyclization of 1,7‐diaryl‐1,6‐diynes and subsequent oxidative photocyclization. The scope of this novel two‐step process was demonstrated by the construction of diverse structures from substrates with various tethers and terminal aryl groups. Late‐stage
α,ω-diynes in the presence of [IrCl(cod)] 2 or [RhCl(cod)] 2 and DPPE gives cyclohexadiene derivatives which are readily aromatized with DDQ or MnO 2 . This two-step procedure gives access to highlysubstituted phthalimides in good yields.