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Please login or sign up for a free trial to access the full content. Method 1: Nucleophilic Substitution Reactions at Phosphorus with Alkali Metal Acetylides

DOI: 10.1055/sos-SD-024-01075

Pietrusiewicz, K. M.; Stankevič, M.Science of Synthesis, (2006241073.

Alkali metal acetylides react with trivalent and pentavalent phosphorus electrophiles at low temperatures to produce phosphorus-functionalized alkynes in good yields. Alkynylmagnesium[‌6‌‌10‌] and alkynyllithium[‌11‌,‌12‌] reagents are usually used, although alkynylcopper,[‌13‌] alkynylsilver,[‌14‌] alkynyltin,[‌15‌] or alkynylzinc[‌16‌] reagents may sometimes give better yields. The alkynylmagnesium and alkynyllithium reagents are conveniently generated from alkynes, haloalkynes, or gem-dihaloalkenes.[‌17‌] For the synthesis of terminally unsubstituted phosphorus-functionalized alkynes, use of trimethylsilyl[‌18‌,‌19‌] or diaminoboryl[‌20‌] derivatives of acetylene as protected equivalents of the parent compound is frequently advantageous. Chlorophosphines, chlorophosphites, and chlorophosphates are typically employed as phosphorus electrophiles. Alkynyllithium reagents are usually preferred for the synthesis of alk-1-ynylphosphites and alk-1-ynylphosphonates (e.g., 1, Scheme 1). These reagents are readily formed at low temperature and can react with chlorophosphites and chlorophosphates at the same temperature. The procedure minimizes the risk of multiple substitutions and affords the desired products in good and reproducible yields (Scheme 1).[‌11‌] Alk-1-ynylphosphoranes are obtained in reactions of phosphonium salts with alkynyllithiums.[‌21‌] Alk-1-ynyldichlorophosphines are formed in good yields by reactions of terminal alkynes with phosphorus trichloride in the presence of an amine as base.[‌22‌]

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