(2-Methoxyethyl)(triphenyl)phosphonium

(2-Methoxyethyl)triphenylphosphonium bromide (CAS: 55894-16-1) is a quaternary phosphonium salt widely used as a reagent in organic synthesis and pharmaceutical research. It consists of a triphenylphosphonium cation with a (2-methoxyethyl) side chain and a bromide counterion, with the molecular formula C₂₁H₂₂BrOP and a molecular weight of 401.28 g/mol .

Physical and Chemical Properties

The compound appears as a white to yellow or off-white crystalline powder. Its melting point is reported at 216 °C, indicating good thermal stability . It has a calculated LogP value of approximately 3.0, which suggests moderate lipophilicity, and the topological polar surface area is 9.23 Ų . The molecule contains six rotatable bonds and no hydrogen bond donors, making it flexible in solution .

Key Applications

This reagent is primarily utilized in the Wittig reaction, where it serves as a precursor for generating phosphonium ylides. In the presence of a strong base, it forms a ylide that reacts with aldehydes or ketones to produce alkenes, offering a reliable method for carbon–carbon double bond formation . The (2-methoxyethyl) group imparts distinct reactivity compared to simpler alkyl analogs such as methyl or ethyltriphenylphosphonium bromide .

Beyond its role in olefination, the compound is employed as an intermediate in the synthesis of pharmaceutical agents. Notably, it is used in the preparation of Triprolidine, an antihistamine with anticholinergic properties for allergy and cold symptom relief . It also serves as a versatile building block in material science and catalysis, where it can act as a phase-transfer catalyst or ligand precursor .

Storage and Handling

The product should be stored at room temperature in a cool, dry, and well‑ventilated area, protected from moisture. It is classified as an irritant (GHS07), with hazard statements H315 (skin irritation), H319 (eye irritation), and H335 (respiratory irritation). Standard laboratory protective equipment should be used during handling .

In summary, (2-Methoxyethyl)triphenylphosphonium bromide is a valuable phosphonium reagent for organic chemists, enabling efficient alkene synthesis via Wittig chemistry and serving as a key intermediate in the production of active pharmaceutical ingredients. Its well‑defined physical properties, commercial availability, and versatile reactivity make it an essential tool in both academic and industrial research settings.