N-oxides and related compounds. Part 58. Some precursors of pyridinium methylide

Abstract

1-t-Butoxycarbonylmethylpyridinium ion (3) is pyrolysed to yield successively the 1-carboxymethyl- and the 1-methyl-pyridinium ions. The intermediate ylide (1) could be trapped by benzaldehyde and other electrophiles.

1-Carboxymethylpyridinium betaine (5) reacts with aldehydes as the ylide tautomer (6) to give products (8) of aldol reactions, transformations of which are described. The reactions of various other electrophiles with the betaine (5) have been investigated.

The ylide (20) from the cation (3) reacts as expected with methyl iodide, benzyl bromide, and benzoyl chloride (at 0 °C). At 25 °C, benzoyl chloride gives a product of further acylation, as do other acid halides.