Cobalt(I)‐Catalyzed Cycloaddition of Functionally Substituted Alkynes and 1,3‐Diynes to 1,3,5,7‐Cyclooctatetraene in the Synthesis of Bicyclo[4.2.2]deca‐2,4,7,9‐tetraenes

Abstract

The [6π+2π]‐cycloaddition of O‐, S‐, N‐, Hal‐, and Si‐containing alkynes and 1,3‐diynes to 1,3,5,7‐cyclooctatetraene was accomplished for the first time using a Co(acac)2‐based four‐component catalytic system [Co(acac)2/dppe/Zn/ZnI2] to give previously undescribed functionally substituted bicyclo[4.2.2]deca‐2,4,7,9‐tetraenes in 72–95% yields. These products are of interest as key monomers for the synthesis of natural and synthetic biologically active compounds.

The Synthesis of Bicyclo[4.2.1]nona-2,4,7-trienes by [6π + 2π]-Cycloaddition of 1-Substituted 1,3,5-Cycloheptatrienes Catalyzed by Titanium and Cobalt Complexes

“…Therefore, we paid attention to the recent studies of Achard et al and our own works dealing with the Co-catalyzed cycloaddition reaction of terminal alkynes with CHT and 1,3,5,7-cyclooctatetraene. , Simultaneously, we set ourselves the task to upgrade cobalt-based catalytic systems known from the literature. Previously, we developed a four-component system, Co­(acac) 2 /dppe/Zn/ZnI 2 , which showed high performance in the cycloaddition of alkynes to 1,3,5-cyclooctatriene and 1,3,5,7-cyclooctatetraene. , However, Co­(acac) 2 is fairly hygroscopic, and therefore, the use of this catalyst for preparative purposes is highly problematic. Therefore, to increase the moisture stability of the catalyst, in the subsequent experiments, we employed the presynthesized Co­(acac) 2 complex with 1,2-bis­(diphenylphosphino)­ethane, Co­(acac) 2 (dppe) .…”

Transition-Metal-Catalyzed Cycloadditions for the Synthesis of Eight-Membered Carbocycles: an Update from 2010 to 2020

“…In this work, Co(acac) 2 was used to replace CoI 2 (Scheme 13, C). [57] In 2020, [6＋2] cycloaddition of azepines with alkynes or dialkynes was also reported (Scheme 13, D). [58] In 2011, Sato and coworkers [59] reported an intramolecular rhodium-catalyzed [6＋2] cycloaddition of 4-allenals with alkynes or alkenes (Scheme 14, A).…”