Methoxycarbonylmethylene-triphenylphosphorane

Reaction of the ylide, generated from the phosphonium salt 578 (from the alcohol 577 and phosphine hydrobromide 504), with the polyene aldehyde 542 gives aleuria-xanthin acetate 579218). The methyl ester of the naturally occurring bixin 586 is formed by a combination of some carbonyl olefinations 279). The acetoxyaldehyde 580 is olefinated with methoxycarbonylmethylene-triphenylphosphorane 67 to the ( )-unsaturated ester 581. The latter is converted into the phosphonium salt 582 upon treatment with triphenylphosphine hydrobromide 504. The corresponding ylide of 582 is reacted with the dialdehyde 539 to the polyene aldehyde ester 583. The latter is reduced and converted into phosphonium salt 584. The corresponding ylide is now reacted in a third carbonyl olefination with 585 to give the methyl ester 586 279> (Scheme 98). 

Photochemical Reactions with Alkoxychromium Carbene Complexes. Photolysis of chromium alkoxycarbene complexes in the presence of tosylmethylene phosphorane [or ester stabilized ylides such as (methoxycarbonylmethylene)-triphenylphosphorane] under an atmosphere of carbon monoxide produced aflenes. Such reactive allenes (EWG at C1 and electron donating group at C3) hydrolyzed to give y-keto-a. -unsaturated sulfones with. stereoselectivity (eq 6). ... 

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