Synthesis, Optical Resolution, and Stereochemical Properties of a Rationally Designed Chiral C–N Palladacycle

Abstract

A novel racemic tertiary amine, 1-(2,5-diisopropylphenyl)-N,N-dimethylethanamine, was synthesized from 2,5-diisopropylbenzaldehyde via a multistep approach in high overall yield. The ortho palladation of this ligand was found to be sensitive to the reaction conditions and the palladating reagents employed. The metal complexation process could thus generate a cyclopalladated complex in high yield, lead to an unexpected N-demethylated amine palladium(II) complex, or both. Both products have been isolated and characterized crystallographically in the solid state and spectroscopically in solution. The racemic cyclopalladated complex could be efficiently resolved via the formation of (S)-prolinato derivatives. The absolute stereochemistries of the resolved diastereomeric complexes were determined by single-crystal X-ray crystallography in the solid state and by 1 H− 1 H rotating frame Overhauser effect (ROESY) NMR spectroscopy in solution. An evaluation of the sterically hindered resolved cyclopalladated units as chiral auxiliaries was conducted in the endo-cycloaddition reaction between 3,4-dimethyl-1-phenylphosphole (DMPP) and ethyl vinyl ketone. The two expected phosphanorbornene adducts were generated with moderate stereoselectivity.

Stereogenic Lock in 1-Naphthylethanamine Complexes for Catalyst and Auxiliary Design: Structural and Reactivity Analysis for Cycloiridated Pseudotetrahedral Complexes

“…It is worth mentioning that a similar cleavage of the C–N bond was observed in one of the byproducts during the attempted cycloiridation of the tertiary amine ( S )- N , N -dimethyl-1-naphthylamine . Such N-demethylation processes are also prevalent if bulky ligands are utilized for cyclometalation …”

Hemilability and structural considerations in complexes of platinum(II) comprising bis(diphenylphosphanyl)methane monoxide, monosulfide, and monoselenide

“…In summary, for the platinum complexes discussed, while the strength of the Pt-E bonds would be expected to increase from O to S to Se, it is also the case that the ring strain increases from O to S to Se. Hence the ease of a � 2 !� 1 !� 2 interconversion depends not only the inherent strength of the Pt-E bond, but the fact that it is offset by the ring strain, such that the rates of interconversion are in the order O > Se > S. Dman complexes have been used in asymmetric syntheses (Yeo et al, 2005;See Leng Yap et al, 2014) and, coupled with hemilabile ligands, they have the potential of improved selectivity. Data collection: PROCESS-AUTO (Rigaku, 1998); cell refinement: PROCESS-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku and Rigaku Americas, 2010); program(s) used to solve structure: SIR92 (Altomare et al, 1994); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al, 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al, 2009).…”

Design, synthesis and applications of chiral functionalized phosphapalladacycles

“…Cyclopalladation reaction of amine 1-(2,5-diisopropylphenyl)-N,Ndimethylethylamine 2n with the bulkier isopropyl group was investigated (Scheme 8). 38 could also be obtained by treatment of 11c-HCl with aqueous NaOH, followed by palladium(II) acetate (1.0 equivalent). Refluxing the mixture of 11c and palladium(II) acetate (1.0 equivalent) in acetone afforded 9c-OAc as well.…”

“…The dimeric ortho-palladated benzylic amine compounds with the bridge readily underwent the coordination reaction of donor ligand, resulting in the bridge-splitting monomeric ortho-palladated complexes. 24,27,[32][33][34][35][38][39][40][41] Triphenylphosphine proved to be one of the best donor ligands, which can easily coordinate to the palladium of the ortho-cyclopalladated complex following the bridge-splitting reaction to form the monomeric complexes 14 (Figure 1). 8-9, 26, 32-35, 38-43 It is also noteworthy, that the complexes 14 often really give X-ray quality crystal.…”