Synthesis and Characterization of Alkyltris(2-pyridyl)phosphonium Salts

Abstract

Alkytris(2-pyridyl)phosphonium salts [(2-Py)were synthesised from (2-Py) 3 P and an excess of RCl. 1c and 1e were found to rapidly decompose in hot acetone to 2,2 -bipyridinium(+1) bromide 2 and (2-Py)P(O)(CH 2 Ph)C(OH)Me 2 3, respectively. A reaction mechanism for both products is proposed. All compounds were fully characterized, including X-ray crystallography for 1a and 3 with 1a being the first representative of this class of compounds characterized by this technique.

Efficient One-Pot Synthesis of Mono- and Bis[di(2-pyridyl)phosphine Oxides] from Tris(2-pyridyl)phosphine

“…Interestingly, decompositions of similar salts in acetone in the absence of alkali gave 2,2′-bipyridine hydrobromide, along with PyP(R)(O)C(Me 2 )OH. 15 Apparently, the formation of the phosphine oxides 3a-f occurs through nucleophilic substitution of one of the pyridyl groups in the organyl[tris(2-pyridyl)]phosphonium cation by a hydroxide anion. In all the above cases, the reaction is strictly chemoselective in terms of the leaving group on the phosphorus atom in 2a-g: no alternative nucleophilic substitution of a benzyl or 2-naphthylmethyl group (or of an alkyl group) by HOwas observed.…”