70052-74-3Relevant academic research and scientific papers
Facile Photochemical Synthesis of Benzylphosphines
Mueller, Gerhard,Waldkircher, Martin,Winkler, Martin
, p. 1606 - 1614 (2007/10/02)
Facile large-scale synthesis of the benzyl-dibromo-phosphines RPBr2 (R = C6H5CH2, 3,5-Me2C6H3CH2, 2-BrC6H4CH2) is accomplished by the photochemical reaction of toluene, mesitylene and 2-bromotoluene, respectively, with PBr3 in the absence of solvent.It the reactions are carried out up to 50percent completion the amount of by-products formed is remarkably low, rarely exceeding 10percent of the total amount of products formed.The selectivity of the photoreaction may be improved up to 98percent if it is carried out in a modified Soxhlet apparatus which allows the predominant irradiation of only the starting materials.The apparent limitations imposed by the low turnovers required to achieve good products formed in a short period of time and by the easy recovery of unreacted starting material by distillation.Thus in the case of 2-BrC6H4CH2PBr2, in a typical run 94 g (261 mmol) of product may be isolated after 2.5 h of irradiation of 970 mmol of 2-BrC6H5CH3 and 1.39 mol of PBr3.In this case the turnover is 32percent, the isolated yield 27percent, and the by-product 2-methylphenyl-dibromo-phosphine only amounts to less than 2percent.The benzyl-dibromo-phosphines are easily methylated with two equivalents of MeMgCl to give the respective benzyl-dimethyl-phosphines in 79-93percent yield.Tertiary benzylphosphines MePRR' (R = 2-BrC6H4CH2, R' = Me3SiCH2; R = R' = 2-BrC6H4CH2) are obtained in easy one-pot syntheses by consecutive reactions of 2-BrC6H4CH2PBr2 with Me3SiCH2MgCl and MeMgCl, and with 2-BrC6H4CH2MgBr and MeMgCl, respectively. - Keywords: Benzylphosphines, Photochemical Synthesis
