Chiral biarylamido/anisole complexes of yttrium in enantioselective aminoalkene hydaroamination/cyclisation |
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Authors: | O'Shaughnessy Paul N Gillespie Kevin M Knight Paul D Munslow Ian J Scott Peter |
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Institution: | Department of Chemistry, University of Warwick, Coventry, UKCV4 7AL. peter.scott@warwick.ac.uk |
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Abstract: | A group of chiral, dibasic, biaryl-bridged amido proligands containing peripheral methoxyphenyl (anisole) ligation are developed for the synthesis of new amide complexes of yttrium and lanthanum. A potentially tetradentate bis(amidoanisole) system gives, on reaction with YN(SiMe(2)H)(2)](3)(THF)] a crystallographically-characterised bis complex Y(H)] presumably as a result of low steric demand, since a more bulky version gives the target YN(SiMe(2)H)(2)](THF)]. The molecular structure of the latter reveals a similar cis-alpha structure to our recently reported Schiff-base analogue. Variable-temperature NMR studies are consistent with low rigidity in the molecular structure. A potentially tridentate, amidoanisolyl/amido proligand gives complexes MN(SiMe(2)H)(2)](THF)(n)](M = Y, n= 1; M = La, n= 2). Chiral non-racemic versions of the above complexes were tested in the hydroamination/cyclisation of 2,2'-dimethylaminopentane to the corresponding pyrrolidine. Activities were relatively low compared to recently reported examples, and ee values were in the range 20-40% despite the well-expressed chirality of the catalysts. |
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