New Synthetic Routes to β‐Olefinic Trialkoxyphosphonium Salts and Phosphonates: Organometallic Variants of the Michaelis‐Arbuzov Reaction

The low‐temperature addition of tertiary phosphites to [(allyl)Fe (CO) 4 ] + X − complexes proceeds regio‐ and stereospecifically and produces metal‐coordinated β‐olefinic trialkoxyphosphonium ions. These can be converted by various routes into the uncomplexed phosphonium salts or phosphonates. Similar reactions of acyclic [(dienyl)Fe(CO) 3 ] + X − compounds give metal‐coordinated (2,4‐dien‐1‐yl)trialkoxyphosphonium salts or dialkyl (2,4‐dien‐1‐yl)phosphonates. The mechanisms and their relationship to the classical Michaelis ‐ Arbuzov reaction are discussed. The new compounds are characterized, if possible, by 1 H‐, 13 C‐, and 31 P‐NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig ‐ Horner reactions, are difficult to obtain by conventional routes.