Synthesis and characterization of polycarbonyl compounds via their BF2-adducts.

A cobalt-catalyzed 1,4-hydrovinylation reaction is the key step in the synthesis of 1,3-dicarbonyl and higher tri- and tetracarbonyl compounds after ozonolysis of the 1,4-diene intermediates. For the isolation and characterization of the products, the 1,3-dicarbonyl subunits were complexed with a BF(2)- or a BR(2)-fragment eliminating the keto-enol tautomerisation. Other 2,3-disubstituted 1,3-butadienes can be generated by a Grubbs enyne metathesis of a symmetrical internal alkyne with ethene. After hydrovinylation and ozonolysis, other 1,3-diketones are accessible.