Sugar-Annulated Oxazoline Ligands: A Novel Pd(II) Complex and Its Application in Allylic Substitution

Abstract

Two novel carbohydrate-derived pyridyl (PYOX)-and cyclopropyl (CYBOX)-substituted oxazoline ligands were prepared from D-glucosamine hydrochloride and 1,3,4,6-tetra-O-acetyl-2-amino-2-deoxy-β-D-glucopyranose hydrochloride in two steps, respectively. The sugar-annulated PYOX ligand formed a stable metal complex with Pd(II), which was fully characterized by NMR spectroscopy and X-ray crystallography. NMR and X-ray analysis revealed a change of the conformation in the sugar moiety upon complexation with the palladium(II) species. Both glycosylated ligands resulted in high asymmetric induction (up to 98% ee) upon application as chiral ligands in the Pd-catalyzed allylic alkylation of rac-1,3-diphenylallyl acetate with dimethyl malonate (Tsuji-Trost reaction). Both ligands provided mainly the (R)-enantiomer of the alkylation product.

d‐Fructose Based Spiro‐Fused PHOX Ligands: Palladium Complexes and Application in Catalysis

“…With the complexes in PhMe as solvent no conversion was obtained (Table , entries 2 and 9). In situ dehalogenation with AgSbF 6 in MeCN as described previously[8a] provided more reactive derivatives of 5 and 6 which showed er 's in a comparable range as for the in situ formed complexes of 1a and 1e with [PdCl(C 3 H 5 )] 2 (Table , entries 4 and 11).…”

“…The reaction has already been studied in detail with other ligands and has often been used as a benchmark test for new ligands. [3e], The allylic alkylation was performed according to a standard procedure with [PdCl(C 3 H 5 )] 2 as palladium source and N , O ‐bis(trimethylsilyl)acetamide (BSA) as base (Scheme ) …”

Multifunctional chiral aminophosphines for enantiodivergent catalysis in a palladium‐catalyzed allylic alkylation reaction

“…69,70 The M and W isomers interconvert readily even at temperatures below 0 71,72 ; however, the ratio can be controlled by ligands with bulky substituents, disfavoring the formation of the W isomers that position the terminal phenyl group of the allyl intermediate closer to the bulkier ligand ( Figure 3A, right panel). [73][74][75] In the case of the P,N-ligands investigated here, it is likely that the M isomer may be favored with the phosphorous center being the ligand side with bulkier substituents ( Figure 3B). The following attack by a nucleophilic species can further contribute to the selectivity because of electronic factors, as the nucleophilic attack tends to prefer the allyl carbon trans to the better π-accepting phosphorous ligating atom ( Figure 3B, Paths a and c preferred over Paths b and d).…”

Synthesis of C2-Symmetric Bisphosphines and Their Application in Enantioselective Transition Metal Catalysis

“…ARBON-CARBON and carbon-heteroatom bonds forming reactions such as allylic substitutions have become part of modern organic chemistry. [1][2][3][4][5][6][7] In this context, there is a remarkable attention in this type of synthesis and over the past few years, extensive researches have been carried out in order to develop efficient chiral ligands. [8][9][10][11][12][13][14][15][16][17][18][19] The first known palladium-catalyzed enantioselective allylic alkylation was introduced by Trost and Strege with moderate enantioselectivities in the presence of chiral 2,3-Oisoproylidene-2,3dihydroxy-1,4-bis(diphenylphosphino)butane (DIOP).…”