Abstract
Abstract Ethoxycarbonyl-triphenylphosphonium bromide reacts with orthoamides of alkynecarboxylic acids 14 to give vinylogous guanidinium bromides, which were transformed to the corresponding tetraphenylborates. In contrast, from CH2-acidic phosphonicesters and orthoamides 14 phosphorylated 1,1-diamino-butadienes can be obtained. Two of these products rearrange to 5-dimethylamino-4-diet-hylphosphono-2,4-hexadienic acid amides upon heating. Reaction of phenylsulfonylated carboxylic acids and alkylketones with orthoamides 14 proceeds under condensation affording 4-phenylsulfonyl-1,1-diamino-1,3-butadienes. Accordingly, the condensation reactions between the orthoamides 14 and isocyanoacetic acid ester deliver 2-isocyano-5,5-bis(dimethylamino)-2,4-pentadienic acid esters. In one of these reactions 5,6-diamino-pyridine-2-carboxylic acid ester is obtained as a by-product. Some of the ketene aminals exist as equilibrium mixtures of stereoisomers, which is a consequence of s-cis and s-trans isomerism of the butadiene unit.
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