Acetic Acid → (+/-) Z 3-(Ethoxycarbonylmethylene)-1-azabicyclo-[2.2.1]heptane oxalate salt

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Reaction Steps

Triethylphosphonoacetate (2.69 g, 0.012 moles) in dry DMF (10 ml) was treated with potassium t-butoxide (1.59 g, 0.013 moles) at 0° C. with continuous stirring under an atmosphere of nitrogen. After 30 minutes (±)1-azabicyclo [2.2.1]heptan-3-one (D6, 1.11 g, 0.01 moles) in DMF (10 ml) was added at 0° C. and the stirred solution allowed to warm to room temperature over a period of 30 min. After standing at room temperature for lh the reaction was neutralised with acetic acid and concentrated in vacuo to a gum. The gum was then partitioned between aqueous potassium carbonate and chloroform. The chloroform solution was separated and concentrated in vacuo to a gum. Kugelrohr distillation in vacuo afforded a colourless oil b.pt 200° C. at 0.5 mm. The oil was dissolved in ether (20 ml) and treated with oxalic acid (900 mg) in methanol (2 ml). The title compound oxalate salt (D1) slowly crystallised out. Recrystallisation from methanol-ether afforded the pure title compound free from the E isomer as needles (D1) (2.13 g; 78%). m.p. 140°-150° C.

Provenance & Evidence