Diynes oxygenative cyclization

Transfer oxygenative cyclization of diynes with DMSO is catalysed by cationic ruthenium complexes. For diynes with terminal aryl groups, [CpRu(AN)3]PF ... 

In previous works this group had observed a competition between the PKR and a [2 + 2 + 2] cyclization in the second reaction step of three triple bonds. Thus, when reacting linear triynes 174 under catalytic, high CO pressure, cobalt mediated PKR conditions, they obtained mixtures of products 175 coming from two [2 + 2 + 1] cycloadditions, and 176 from a [2 + 2 + 1]/ [2 + 2 + 2] tandem reaction. When the triple bonds were ether linked, the latter was the favored reaction, while with substrates lacking oxygen atoms, the iterative PKRs was the major pathway (Scheme 51) [166]. When the reaction was performed intramolecularly between a diyne and an alkyne, the only reaction products were the result of a [2 + 2 + 1 ]/[2 + 2 + 2] tandem cycloaddition [167,168]. 

The couplings of 1,6- and 1,7-intemal diynes or oxygen-linkage mixed terminal/internal diyne with isocyanides provide useful entries for constructing bicydic cydopentenone skeletons [152]. The cyclizations of symmetric or unsymmetric diynes bearing amine moiety at the tethered chain proceeded with modest to good regioselectivity in acceptable isolated yield [151,153]. 

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