Molybdenum enolates aldol reaction

The achiral molybdenum enolate 2 reacts with benzophenone and benzaldehyde at —78 °C to yield the x,/i-unsaturated molybdenum-acyl complexes34, which presumably arise via elimination of hydroxide from unobserved aldolate intermediates such as 3. No examples of such aldol reactions with complexes that are chiral at molybdenum have been reported. 

The enolates (48) and (49) of the transition metals tungsten, rhenium and molybdenum can be successfully prepared by the nucleophilic displacement of a-chloro ketones and a-chloro esters with the appropriate transition metal anion (Scheme 6). They are isolated as C-bound enolate derivatives and, except for the rhenium enolate (49), do not undergo thermal aldol additions to benzaldehyde. However, Bergman and Heathcock et al. have found that an aldol reaction of complex (48) with benzaldehyde can occur on irradiation via the rearranged q -oxaallyl derivative (50), where the metal aldolate (51) can then be... 

Molybdenum and tungsten C-enolates can be generated by reaction of complexes with a-chlorocarbo-nyls (Scheme 67). These 2-oxaallyl(T) -C-enolate) complexes react with aldehydes in a photoreaction to produce aldol products, by way of the ii -enolate. 

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