New Developments in Stereoselective Palladium-Catalyzed Allylic Alkylations of Preformed Enolates

Braun, Manfred; Meier, Thorsten

doi:10.1055/s-2006-933138

Cited by 60 publications

(10 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The new chelating anions are generated using the bridging hydroxide ligand, and we note that related enolate complexes of palladium have been reported by several groups. [27][28][29][30][31] Solution Structures. The reaction of 2 with, for example, imide 4 produces 1 equiv of water via the deprotonation of the weakly acidic NH proton and the generation of Pd(II) salts 9-11.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, X-ray, and NMR Studies on Palladium BINAP Complexes Containing Oxazolidinone and Acetylacetonate Anions

and¹,

Pregosin²,

Albinati³

et al. 2007

Organometallics

View full text Add to dashboard Cite

A series of monocationic palladium BINAP complexes, [Pd(rac-BINAP)(an oxazolidinone anion)] [X] and [Pd(rac-BINAP)(an acetylacetonate anion)][X] (X ) a, CF 3 SO 3 -; b, BF 4 -) (9-13), have been synthesized and characterized. A dicationic intermediate, pertinent to the Pd-catalyzed hydroamination reaction, arising from the reaction of the bis-aquo complex [Pd(H 2 O) 2 (rac-BINAP)] 2 (CF 3 SO 3 ) 2 and 1 equiv of an oxazolidinone, has been characterized via low-temperature NMR studies. The structures of the complexes [Pd(rac-BINAP)(, 12b, and [Pd(µ-OH)(rac-BINAP)] 2 (CF 3 SO 3 ) 2 have been determined by X-ray diffraction. The solid-state structures of two separate forms of the BF 4 -salt 12b were obtained. One form of the salt can be thought of as a tight ion pair, whereas the second form contains a dichloromethane solvent molecule, packed in approximately a fifth coordination position together with a relatively remote BF 4 -anion. These structures represent a rare example where both ion pairing and strong solvation could be individually characterized. PGSE diffusion coefficients (D values) were measured for both the CF 3 SO 3 -and BF 4 -salts of 9-13 in CD 2 Cl 2 . In addition, D values were obtained for the CF 3 SO 3 -salts in THF and CDCl 3 solutions. The amount of ion pairing decreases in the sequence CDCl 3 > THF > CD 2 Cl 2 . The 1 H, 19 F-HOESY spectra for the salts in CDCl 3 suggest that the CF 3 SO 3 -is approaching the positive metal and phosphorus centers via a pathway that brings it closest to the P-phenyl groups but remote from the chelating anion.

show abstract

Section: Resultsmentioning

confidence: 99%

Synthesis, X-ray, and NMR Studies on Palladium BINAP Complexes Containing Oxazolidinone and Acetylacetonate Anions

and¹,

Pregosin²,

Albinati³

et al. 2007

Organometallics

View full text Add to dashboard Cite

show abstract

“…Im Zusammenhang mit der katalytischen Alkylierung von Keton-und Esterenolaten durch Allyl-oder Benzylelektrophile [172][173][174][175][176] [43] Die Aktivität von Me 2 AlNTf 2 in Mukaiyama-Aldolreaktionen mit sehr guten Ausbeuten wurde außerdem in der Kreuzaldolreaktion von Ketonacceptoren und in der Mukaiyama-Michael-Addition an Enone gezeigt. Der analoge sperrige Bis(2,6-diphenylphenoxid)aluminiumtriflimidatKomplex wurde erfolgreich zur chemoselektiven Aktivierung von weniger gehinderten Aldehyden verwendet (Schema 48).…”

Section: Elektronenreiche Alkene Und Enolate Als Nucleophileunclassified

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

2010

View full text Add to dashboard Cite

Der steigende Bedarf an neuen selektiven und umweltverträglichen Methoden in der organischen Synthese treibt die Entwicklung effizienterer Reaktionssysteme an. In diesem Zusammenhang hat man sich häufig auf Übergangsmetalle, Liganden und Additive konzentriert; dem Gegenion des Metallkations wurde weniger Aufmerksamkeit geschenkt. Kürzlich wurden Metallsalze mit einem oder mehreren Triflimidat‐Gegenion(en) (Tf2N−) beschrieben. Triflimidate bilden eine einzigartige Katalysatorklasse mit außergewöhnlicher σ‐ und π‐Lewis‐Acidität, die durch die starke Delokalisierung der Ladung im Triflimidation sowie seine sterische Hinderung begründet wird. Daher wird praktisch kein nucleophiles Verhalten und eine hohe positive Ladungsdichte am Metallkation beobachtet, die seine Lewis‐Acidität verstärkt. Folglich sind Metalltriflimidate häufig effizienter als entsprechende ‐halogenide oder ‐triflate. Dieser Aufsatz beschreibt Methoden zur Herstellung von Metalltriflimidaten und deren Einsatz als Katalysatoren.

show abstract

“…asymmetric synthesis | organocatalysis T he enantioselective catalytic α-alkylation of simple ketones remains a fundamental goal in chemical synthesis (1)(2)(3)(4). Seminal work from Doyle and Jacobsen (5), Trost and co-workers (6)(7)(8), Stoltz and co-workers (9, 10), Braun and co-workers (11,12), and Hartwig and co-workers (13,14) has introduced valuable previously undescribed technologies for (i) the enantioselective alkylation of preformed or in situ generated metal enolates (5,6,(11)(12)(13)(14)(15)(16)(17) and (ii) the asymmetric and decarboxylative conversion of allyl keto carbonates to α-allylated ketones (7)(8)(9)(10).…”

mentioning

confidence: 99%

Direct and enantioselective α-allylation of ketones via singly occupied molecular orbital (SOMO) catalysis

Mastracchio

Warkentin

Walji

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

111

View full text Add to dashboard Cite

The first enantioselective organocatalytic α-allylation of cyclic ketones has been accomplished via singly occupied molecular orbital catalysis. Geometrically constrained radical cations, forged from the one-electron oxidation of transiently generated enamines, readily undergo allylic alkylation with a variety of commercially available allyl silanes. A reasonable latitude in both the ketone and allyl silane components is readily accommodated in this new transformation. Moreover, three new oxidatively stable imidazolidinone catalysts have been developed that allow cyclic ketones to successfully participate in this transformation. The new catalyst platform has also been exploited in the first catalytic enantioselective α-enolation and α-carbooxidation of ketones.asymmetric synthesis | organocatalysis T he enantioselective catalytic α-alkylation of simple ketones remains a fundamental goal in chemical synthesis (1-4). Seminal work from Doyle and Jacobsen (5), Trost and co-workers (6-8), Stoltz and co-workers (9, 10), Braun and co-workers (11,12), and Hartwig and co-workers (13, 14) has introduced valuable previously undescribed technologies for (i) the enantioselective alkylation of preformed or in situ generated metal enolates (5,6,(11)(12)(13)(14)(15)(16)(17) and (ii) the asymmetric and decarboxylative conversion of allyl keto carbonates to α-allylated ketones (7-10). With these key advances in place, a goal now for asymmetric catalysis has become the direct α-allylation of simple ketone substrates (18,19), an elusive yet potentially powerful bond construction (Scheme 1).Recently, we questioned whether the catalytic principles of singly occupied molecular orbital (SOMO) activation (20) might be translated to ketonic systems, thereby providing an unreported mechanism for direct and enantioselective α-carbonyl alkylation. Despite the superficial similarities between aldehydes and ketones, these carbonyl families exhibit largely different steric and electronic properties with respect to catalyst interactions. As a consequence, the translation of enantioselective activation modes between these carbonyl subclasses is often difficult (if not unattainable in many cases) (21,22). Herein, we describe the invention of a previously undisclosed family of organocatalysts that enable cyclic ketones to successfully function within the SOMO-activation platform while being chemically robust to oxidative reagents. Moreover, we document the introduction of a previously undescribed catalytic α-ketone alkylation reaction that is immediately amenable to asymmetric induction. Enantioselective SOMO CatalysisOver the last decade, the field of enantioselective synthesis has witnessed tremendous progress in the successful implementation of small organic molecules as asymmetric catalysts. In particular, two modes of carbonyl activation by chiral secondary amines have led to the discovery of a large number of previously undescribed reactions (Scheme 2): (i) Iminium catalysis (23), wherein lowest unoccupied molecular orbital (LUMO) lowering a...

show abstract

New Developments in Stereoselective Palladium-Catalyzed Allylic Alkylations of Preformed Enolates

Cited by 60 publications

References 33 publications

Synthesis, X-ray, and NMR Studies on Palladium BINAP Complexes Containing Oxazolidinone and Acetylacetonate Anions

Synthesis, X-ray, and NMR Studies on Palladium BINAP Complexes Containing Oxazolidinone and Acetylacetonate Anions

Metalltriflimidate sind bessere Katalysatoren für die organische Synthese als Metalltriflate – der Effekt eines stark delokalisierten Gegenions

Direct and enantioselective α-allylation of ketones via singly occupied molecular orbital (SOMO) catalysis

Contact Info

Product

Resources

About