NEW SYNTHESIS AND REACTIONS OF UNSATURATED HETEROTITANACYCLES

Dicarbonyltitanocene reacts chemoselectively with difunctional carbonyl compounds such as 1,2-diketones and 1,4-diketo-2-enes, with alpha-ketothioketones, alpha-ketoimines and azodicarbonic esters and -amides to yield the corresponding, mostly new, heterotitanacycles that are capable of a lot of useful follow-up reactions. These chelate complexes, containing three to four heteroatoms, allow the substitution of the entire titanocene fragment by carbon (formation of vinylenic carbonates and the thia-derivatives of these) or by further heteroatoms like boron or phosphorus (formation of boroles and phosphonic acid derivatives), thus retaining the cyclofunctionality. Alternatively, some of the new chelate complexes can be readily C-C-chain-lengthened via a deprotonating/alkylating sequence, leaving the metallacycle unaffected.