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 ¹H-, ¹³C-, and ³¹P-NMR spectra. The new phosphonium salts and phosphonates, potentially useful for Wittig-Horner reactions, are difficult to obtain by conventional routes.