Mechanism of stereoinduction in asymmetric synthesis of highly functionalized 1,2-dihydroquinolines and 2H-1-benzopyrans via nonracemic palladacycles with a metal-bonded stereogenic carbon

The Journal of Organic Chemistry
Genliang Lu, Helena C Malinakova

Abstract

To establish the synthetic utility of palladacycles, a stable racemic benzannulated azapalladacycle featuring a palladium-bonded sp(3)-hybridized stereogenic carbon was prepared and converted into a series of racemic 2,3,4-trisubstituted 1,2-dihydroquinolines via a regioselective insertion of activated alkynes (RCCCOOEt). Analogous diastereomerically enriched azapalladacyle (92% de) and oxapalladacycle (64% de) were synthesized from arylpalladium(II) iodo complexes possessing a nonracemic spectator ligand ((1R,2R)-N,N,N',N'-tetramethyl-1,2-diaminocyclohexane) via an intramolecular displacement of the iodide by an ester enolate. Absolute configurations of the metal-bonded stereocenters in the diastereomerically enriched palladacycles were unequivocally assigned, and the efficiency of stereoinduction was systematically studied. On the basis of these experiments, a plausible mechanism for the transfer of chirality from the nonracemic auxiliary ligand to the palladium-bonded stereogenic carbon was proposed. A restricted rotation about the palladium-aryl bond in arylpalladium(II) iodo complexes giving rise to atropisomers, as well as the nature of the leaving group (iodide or acetate), were found to play a crucial role in the chiral...Continue Reading

References

Nov 1, 1974·Journal of Agricultural and Food Chemistry·R D TrepkaJ T Waddington
Feb 14, 2002·Journal of the American Chemical Society·Takayuki HamadaStephen L Buchwald
Apr 4, 2002·Journal of the American Chemical Society·Dirk J Spielvogel, Stephen L Buchwald
Oct 12, 2002·Organic Letters·Janelle L Portscheller, Helena C Malinakova

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Citations

Apr 28, 2011·Acta Crystallographica. Section E, Structure Reports Online·Zeynep KeleşoğluOrhan Büyükgüngör
Jul 3, 2009·Journal of the American Chemical Society·Rebecca Keller Friedman, Tomislav Rovis
Dec 14, 2016·Chemical Communications : Chem Comm·Ana I Ojeda-AmadorCharles T O'Hara
Dec 18, 2007·Chemical Reviews·Jean-Claude Kizirian
Jul 2, 2011·Organic Letters·Matthew G Beaver, Timothy F Jamison
Mar 19, 2011·The Journal of Organic Chemistry·Krishnendu BeraUmasish Jana

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