Application of Transmetalation to the Synthesis of Planar Chiral and Chiral-at-Metal Iridacycles

Ross A. Arthurs, David L. Hughes, Peter N. Horton, Simon J. Coles, Christopher J. Richards

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Abstract

Diastereoselective lithiation of (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline followed by addition of HgCl2 resulted in the formation by transmetallation of an (S,Sp)-configured mercury substituted complex. Addition to this of [Cp*IrCl2]2 and tetrabutylammonium chloride resulted in a second transmetallation reaction and formation of an (S,Sp,RIr)-configured chloride-substituted half-sandwich iridacycle as exclusively a single diastereoisomer. By reversing the lithiation diastereoselectivity by use of a deuterium blocking group an alternative (S,Rp,SIr)-configured iridacycle was synthesised similarly. Use of (R)-Ugi’s amine as substrate in the lithiation/double transmetallation sequence gave a (R,Sp,SIr)-configured half-sandwich iridacycle, complexes of this type being previously unavailable by direct cycloiridation. Lithium to gold transmetallation was also demonstrated with the synthesis of an (S,Sp)-configured Au(I) ferrocenyloxazoline derivative. Use of the (S,Rp,SIr)-iridacycle as a catalyst for the formation of a chiral product by reductive amination with azeotropic HCO2H/NEt3 resulted in a racemate.
Original languageEnglish
Pages (from-to)1099–1107
JournalOrganometallics
Volume38
Issue number5
Early online date18 Feb 2019
DOIs
Publication statusPublished - 11 Mar 2019

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