NEW SYNTHESIS AND REACTIONS OF UNSATURATE D HETEROTITANACYCLES

Dicarbonyltitanocene reacts chemoselectively with difunctional carbony l compounds such as 1,2-diketones and 1,4-diketo-2-enes, with alpha-ke tothioketones, alpha-ketoimines and azodicarbonic esters and -amides t o yield the corresponding, mostly new, heterotitanacycles that are cap able of a lot of useful follow-up reactions. These chelate complexes, containing three to four heteroatoms, allow the substitution of the en tire titanocene fragment by carbon (formation of vinylenic carbonates and the thia-derivatives of these) or by further heteroatoms like boro n or phosphorus (formation of boroles and phosphonic acid derivatives) , thus retaining the cyclofunctionality. Alternatively, some of the ne w chelate complexes can be readily C-C-chain-lengthened via a deproton ating/alkylating sequence, leaving the metallacycle unaffected.