The Reaction of Butadienylphosphonates with a Oxosulfonium Ylide, Phosphonium Ylides, and Ketone Enolates

The condensation of diethyl (ethoxycarbonylmethyl)phosphonate (1a) with cinnamaldehyde in the presence of piperidine gave a 1:1 mixture of diethyl (1E,3E)- (2a) and (1Z,3E)-(1-ethoxycarbonyl-4-phenyl-1,3-butadienyl)phosphonates (2b) in 82% yield, while a similar reaction using diethyl [cyanomethyl- (1b) and methylsulfonylmethyljphosphonates (1c) exclusively gave diethyl (1E,3E)-[1-cyano- (3) and 1-methyl-sulfonyl-4-phenyl-1,3-butadienyl]phosphonates (4) in 78% and 93% yields, respectively. The reaction of the butadienylphosphonates 2–4 with dimethyloxosulfonium methylide (5) gave mixtures of (E)- and (Z)-(1-substituted 2-styrylcyclopropyl)phosphonates 7–9 in good yields. Similar treatment of the butadienylphosphonate 2 with phosphonium ylides 16a–c led to (3-substituted 1-ethoxycarbonyl-2-styrylcyclopropyl)phosphonates 17a–c in moderate yields. Reduction and oxidation of 7 were studied. The reaction of the phosphonates, 2 and 4, with ketone enolates and ketones resulted in the formation of unexpected olefins 22–24 and dienes 20a, b. The reaction mechanism is discussed.