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Synthesis of Phosphanyl Sulfoximines Through Phospha‐Michael Reaction of Alkenyl Sulfoximines and Their Evaluation as Chiral Bidentate 1,5‐N,P Ligands for Palladium in Asymmetric Allylic Alkylation
Author(s) -
Lemasson Fabien,
Gais HansJoachim,
Runsink Jan,
Raabe Gerhard
Publication year - 2010
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200901462
Subject(s) - chemistry , tsuji–trost reaction , allylic rearrangement , dimethyl malonate , alkylation , stereochemistry , medicinal chemistry , ligand (biochemistry) , denticity , enantioselective synthesis , chiral ligand , chirality (physics) , crystal structure , organic chemistry , catalysis , biochemistry , nambu–jona lasinio model , receptor , chiral symmetry breaking , physics , quantum mechanics , quark
The intermolecular phospha‐Michael reaction of cyclic and acyclic alkenyl sulfoximines proceeds readily and yields the corresponding phosphanyl sulfoximines in good yield. The asymmetric induction provided by sulfoximine group in C–P bond formation is apparently only low. The configuration of three phosphanyl sulfoximine–boranes has been determined by X‐ray crystal structure analysis. The ability of the phosphanyl sulfoximines to act as ligand in Pd‐catalyzed asymmetric allylic alkylation was studied with pairs of diastereomeric cyclic and acyclic derivatives carrying different substituents at the N atom. This study showed that the substituent at the N atom and both the chirality of the backbone and sulfoximine group play a crucial role in determining the enantioselectivity of the allylic alkylation. The Pd‐catalyzed reaction of the racemic 1,3‐diphenylallyl acetate with the malonate anion in the presence of a cyclic N ‐benzyl‐substituted phosphanyl sulfoximine gives the corresponding malonate with 97 % ee in 98 % yield. The similar alkylation with dialkyl‐substituted allylic acetates proceeds only with medium enantioselectivity. The bidentate 1,5‐N,P‐coordination of the Pd atom by the phosphanyl sulfoximine was confirmed by NMR experiments of a π‐1,3‐diphenylallyl‐Pd II complex containing a cyclohexyl phosphanyl sulfoximine as ligand. The cyclohexane ring of the free cyclic phosphanyl sulfoximines adopts in solution and in the crystal a conformation in which the sulfoximine and phosphanyl group are both in a pseudo axial position. The coordination of the ligand to the Pd atom causes an inversion of the cyclohexane ring, which places the two groups in equatorial position.