Formation of Eight-Membered Ring Systems by Annulation

2 Formation of Eight-Membered Ring Systems by [4+2+2] Annulation 

The nickel-catalyzed intermolecular reaction [4+2+2]-annulation of diynes with cyclobutanone as C4 fragment includes the ring expansion 

2- ylidene] increases the catalytic activity of nickel(O), and the reaction takes place at room temperature, to give the product 2.270 in 92% yield. The structure of the latter was established by NMR spectroscopy ( H, NOESY, HMQC, and HMBC). Formation of six-membered rings is probably a result of the parallel reaction of [4-f2]-annulation. 

3- elimination, changing the seven-membered ring to the nine-membered 

3 AuBrs (AICI3)- and Cu(OTf)2-Catalyzed [4+2] Cycloaddition of Alkynyl- and Alkenyl-Enynones and Enynals An Approach to Eunctionalized Polycyclic Hydrocarbons 

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