Pyrrolizines with nucleophiles

Vinylphosphonium salts accept nucleophiles by addition in a Michael reaction to form phosphoranes, which may subsequently react with a carbonyl group to form an alkene (see Scheme 10). This reaction, discovered by E. E. Schweizer in 1964,80 was developed into a widely applicable cycliza-tion method.81 The reaction of 2-formyIpyrrole with vinyltriphenylphos-phonium bromide to give 87% of 3/f-pyrrolizine (1) is among the first to... 

Not surprisingly, the anion derived from 3//-pyrrolizine is a stronger nucleophile than compound 1 itself. Thus the anion reacts with deuterium oxide to give 31//,32//-pyrrolizine, but attempts at further enrichment give mixed deuteriopyrrolizines.83,115 The anion reacts with ketones to give azafulvenes such as 248 and 268.43,115 It seems possible that the reported formation of the oxime of 3//-pyrrolizin-3-one (269) from 3//-pyrrolizine and... 

Nucleophilic additions occur at IH-pyrrolizin-l-ones that contain electron-withdrawing substituents at position 2. Pyrrolizinone (31) adds alcohol and dimethylamine, respectively, to give adducts (32). The chloro compound (33) is reported to react with malononitrile giving (34) although the chemical shift of H-3 (6.22 ppm) seems hard to justify <82CB706>. 

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