REACTION OF TUNGSTEN ETA(3)-ANTI-PENTADIENYL COMPOUNDS WITH REACTIVE OLEFINS AND ISOCYANATES - [5+2]CYCLOADDITION VERSUS ACYLATION

Sequential treatment of CpW(CO)(3)(CH2C=CCMe=CH2) (1) with CF3SO3H and MeOH in cold diethyl ether (-40 degrees C) gave a 75% yield of (CO)(3 )(eta(3)-anti-2-CO(2)Me-4-methylpentadienyl) (2). Compound 2 reacted w ith TCNE to afford the novel [5 + 2] cycloaddition adduct 3 in 62% yie ld; the molecular structure of 3 showed a 1,2-shift of the tungsten fr agment, indicating a eta(4)-s-cis-diene reaction intermediate. The rea ction of 2 with reactive isocyanates RN=C=O (R = PhSO(2), CH3C6H4SO2) in cold CH2Cl2 produced 4a (R = PhSO(2)) and 4b (R = CH3C6H4SO2) in 82 % and 87% yields, respectively; the two compounds can be regarded as t he acylation derivatives of 2, according to an X-ray diffraction study of 4a.