Aufbau von Heterocyclen durch -Cycloaddition von Uebergangsmetall-koordinierten Heteroolefinen mit Butadienen: zur Regioselektivitaet der Cycloaddition

Article abstract of DOI:10.1016/0022-328X(89)85340-9

The pentacarbonyl(thioaldehyde), -(selenoaldehyde), and -(selenoketone) complexes (CO)5M (I) (M = Cr: X = S, R = H (a); M = W: X = S, R = H (b); X = Se, R = H (c); X = Se, R = Ph (d)) react with 2,3-dimethyl-1,3-butadiene by <4 + 2>-cycloaddition to give the metal-coordinated thia- and selenacycles, (CO)5M (IIIa-d).The Structure of IIId was established by an X-ray diffraction study.The reactions of Ia with 2-methyl-1,3-butadien (IV) and of Ia and Ib with trans-penta-1,3-diene (VI) are regioselective.The cycloaddition of IV to Ia yields the two isomers (CO)5Cr or (CO)5M in the ratio 2.4/1 (M = Cr) or 3/1 (M = W), respectively.The thiacycle can be cleaved from the metal intact by oxidation of IIIa with (NH4)2 in acetone.