SYNTHESIS AND PROPERTIES OF TETRAKIS(UREIDOMETHYL)PHOSPHONIUM SALTS

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Abstract
Hydroxymethylphosphonium salts such as (HOCH2)4PCl (1), Ph3P(CH2OH)Cl (5), or (HOCH2)4PI (8) condense with urea and its methyl derivatives, giving stable ureidomethylphosphonium salts in which the quaternary structure is preserved. With few exceptions, ureas are too feebly basic to cause the dissociation to tertiary phosphine and formaldehyde that characterizes the reactions of hydroxymethylphosphonium salts with primary or secondary amines. The chemistry of the ureidomethylphosphonium salts is explored, particularly with respect to their physical and spectral properties, ion exchange, and hydrolysis with acid or base. If the phosphonium salt contains a hydrogen substituent on N-1, hydrolysis with alkali follows a β-elimination pathway, giving the tertiary phosphine, but if the N-1 position is blocked by a methyl group, the reaction follows the Cahours-Hofmann pathway, giving the tertiary phosphine oxide.