REDUCTION OF ALPHA,BETA-UNSATURATED KETONES AND ALDEHYDES BY TUNGSTEN-TUNGSTEN TRIPLE BONDS - FORMATION OF 1,2 AND 1,4 ADDUCTS AS OPPOSED TO C=O CLEAVAGE

Whereas reactions between sterically unencumbered aldehydes RCHO and [W2(OCH2Bu(t))6(py)2] (py = pyridine) yield mu-alkylidene oxo ditungsten compounds, similar reactions with the alpha,beta-unsaturated organic carbonyls CH2 = CHCH = O, MeCH = CHCH = O and CH2CHC(Me) = O give 2:1 adducts of three different structural types; the presence of the neighbouring C-C double bond allows chelate behaviour by ring-closure, thereby providing a kinetic diversion from the otherwise facile C = O bond cleavage.