Acetylenic amides. 2. The generation and reactions of dianions derived from 2‐propynamides

Abstract The dianion of N ‐benzyl‐2‐propynamide can be generated by the treatment of 4 with two equivalents of LDA at −65° or ethylmagnesium bromide at −20°. The trilithio species 6 is readily formed using 3 equivalents of LDA. Reaction of 5 with aldehydes or ketones produce hydroxypropynamides 9 in good yields. Silation of 5a with chlorotrimethylsilane produces N ‐benzyl‐3‐trimethylsilyl‐2‐propynamide ( 13 ) in high yield. Reduction of 9 furnishes either fully saturated amides 15 or partially reduced cis ‐olefins 16 or 18 . Compounds 16 , on heating, rearrange to 4‐ketoamides 17 . Carboxylation of 5a with carbon dioxide produces 3‐benzyl‐2,4‐dioxo‐5‐oxazidinylacetic acid ( 11 ). Warming 11 in dimethyl sulfoxide results in the loss of carbon dioxide and the formation of N ‐benzylpyruvamide ( 21 ).