Enantiomerically Pure Phosphaalkene–Oxazolines (PhAk‐Ox): Synthesis,Scope and Copolymerization with Styrene |
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Authors: | Julien Dugal‐Tessier Spencer C Serin Emmanuel B Castillo‐Contreras Dr Eamonn D Conrad Prof?Dr Gregory R Dake Prof?Dr Derek P Gates |
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Institution: | Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, V6T 1Z1 (Canada), Fax: (+1)?604‐822‐2847 |
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Abstract: | The design of a synthetic route to a class of enantiomerically pure phosphaalkene–oxazolines (PhAk‐Ox) is presented. The condensation of a lithium silylphosphide and a ketone (the phospha‐Peterson reaction) was used as the P?C bond‐forming step. Attempted condensation of PhC(?O)Ox (Ox=CNOCH(iPr)C H2) and MesP(SiMe3)Li gave the unusual heterocycle (MesP)2C(Ph)?CN‐(S)‐CH(iPr)CH2O ( 3 ). However, PhAk‐Ox (S,E)‐MesP?C(Ph)CMe2Ox ( 1 a ) was successfully prepared by treating MesP(SiMe3)Li with PhC(?O)CMe2Ox (52 %). To demonstrate the modularity and tunability of the phospha‐Peterson synthesis several other phosphaalkene–oxazolines were prepared in an analogous manner to 1 a : TripP?C(Ph)CMe2Ox ( 1 b ; Trip=2,4,6‐triisopropylphenyl), 2‐iPrC6H4P?C(Ph)CMe2Ox ( 1 c ), 2‐tBuC6H4P?C(Ph)CMe2Ox ( 1 d ), MesP?C(4‐MeOC6H4)CMe2Ox ( 1 e ), MesP?C(Ph)C(CH2)4Ox ( 1 f ), and MesP?C(3,5‐(CF3)2C6H3)C(CH2)4Ox ( 1 g ). To evaluate the PhAk‐Ox compounds as prospective precursors to chiral phosphine polymers, monomer 1 a and styrene were subjected to radical‐initiated copolymerization conditions to afford {MesPC(Ph)(CMe2Ox)}x{CH2CHPh}y]n ( 9 a : x=0.13n, y=0.87n; GPC: Mw=7400 g mol?1, PDI=1.15). |
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Keywords: | asymmetric synthesis inorganic polymers main group elements phosphaalkenes phosphorus polymers |
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