Novel Chiral Biheteroaromatic Diphosphine Oxides for Lewis Base Activation of Lewis Acids in Enantioselective Allylation and Epoxide Opening

Simonini, Valentina; Benaglia, Maurizio; Benincori, Tiziana

doi:10.1002/adsc.200700564

Cited by 54 publications

(19 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Noteworthy, a more electron poor chiral phosphine oxide, such as BITIANPO 3 , promoted the reaction in very low yield (9%), although with good diastereo‐ and enantioselectivity (96/4 syn/anti , 79% ee ). These results confirm a trend already observed in the chiral Lewis base‐promoted enantioselective addition of allyltrichlorosilane to aldehydes20 and pointed to the importance of the electronic properties of the chiral phosphine oxide in fine‐tuning the catalyst’s performance.…”

Section: Methodssupporting

confidence: 88%

Organocatalytic Stereoselective Direct Aldol Reaction of Trifluoroethyl Thioesters

et al. 2011

Self Cite

View full text Add to dashboard Cite

The first organocatalytic, stereoselective and direct aldol reaction of activated thioesters with aldehydes has been accomplished. The trichlorosilyl ketene thioacetal generated in situ by adding a tertiary amine to a trifluoroethyl thioester in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomerically pure biheteroaromatic phosphine oxide to react with different aldehydes, coordinated to as well as activated by the chiral cationic hypervalent silicon species. Starting from a variety of readily available thioesters, this Lewis acid-mediated Lewis base-catalyzed transformation allows the direct synthesis of syn-b-hydroxy thioesters in up to 95% ee.Keywords: aldol reaction; organocatalysis; phosphine oxides; tetrachlorosilane; thioesters The development of a direct diastereo-and enantioselective, catalytic aldol reaction of esters with carbonyl derivatives remains one of the unsolved challenges in organocatalysis.[1] The difficulty of successfully realizing such a transformation arises from the lower acidity of the a protons of carboxylic esters compared to those of a ketone or an aldehyde. Indeed, the pK a value for ester derivatives (ca. 19) [2] is significantly higher than that (ca. 16-17) necessary to activate a nucleophilic substrate via amine catalysis.[3] Since reactions with donors in the ester oxidation state via an enamine-based organocatalytic approach are not feasible, [4] and thioesters may react with a secondary amine to afford the corresponding amide, activation of the ester nucleophile is necessary. Taking inspiration from Nature, a few groups have recently studied the possibility to perform catalytic stereoselective transformations with malonic acid hemithioesters, exploiting either organometallic or metal-free catalysis. For the organometallic approach Shairs group and ours [5a,b] have investigated the use of chiral copper(II) complexes in the malonic acid hemithioester addition to aldehydes. Studying the metal-free methodology Riccis group has realized a decarboxylative addition to imines catalyzed by a readily available Cinchonabased compound to afford b-amino thioesters in up to 79% ee [6] At the same time, Wennemers showed that a bifunctional thiourea derivative of a Cinchona alkaloid could efficiently promote the enantioselective 1,4-addition of malonic acid hemithioesters to nitro-A C H T U N G T R E N N U N G olefins under mild conditions and in up to 90% ee [7] More recently, Ricci and Bernardi reported an efficient stereoselective Mannich reaction of sulfonylacetates with N-carbamoylimines under phase-transfer catalysis conditions in the presence of a quinine-derived chiral ammonium salt; [8] in this case, further synthetic elaboration was necessary to convert the reaction products into b-amino esters.An alternative approach has been recently investigated by Barbas who introduced the use of trifluoroethyl thioesters as activated nucleophilic substrates suitable for organocatalytic amine activation. [9] In the attempt to have access to a set of r...

show abstract

Section: Methodssupporting

confidence: 88%

Organocatalytic Stereoselective Direct Aldol Reaction of Trifluoroethyl Thioesters

et al. 2011

Self Cite

View full text Add to dashboard Cite

show abstract

“…This indicated that the substituents on the phenyl ring had a remarkable effect on the enantioselectivities in the desymmetrization of meso -epoxides [84]. Benaglia [85] and colleagues have developed chiral phosphine oxides OC-64 and OC-69 for the enantioselective desymmetrization of meso -stilbene oxide to provide the corresponding vicinal chlorohydrin 96 in up to 82% ee.…”

Section: Reviewmentioning

confidence: 99%

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

Wang¹

2013

Beilstein J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…We were interested in applying our catalytic methodologies to the transformation; in our previous studies of Lewis‐based catalyzed reactions in the presence of silicon tetrachloride the use of biheteroaromatic diphosphine oxides, more electron‐rich than the commonly used binaphthyl diphosphine derivatives, has often led to the formation of the desired products with enantioselectivities higher than those obtained with BINAPO; therefore we decided to investigate the behavior of ( S )‐tetramethyl‐bithiophene phosphine oxide, ( S )‐TetraMe‐BITIOPO, in the direct double aldol reaction between aryl methyl ketones and aromatic aldehydes.…”

Section: Introductionmentioning

confidence: 99%

Enantiomerically Pure Bithiophene Diphosphine Oxides as Catalysts for Direct Double Aldol Reactions

et al. 2013

Self Cite

View full text Add to dashboard Cite

The direct aldol reaction between aryl methyl ketones with aromatic aldehydes in the presence of tetrachlorosilane and a catalytic amount of a chiral bithiophene diphosphine oxide was studied; the product of double aldol addition was isolated as diacetate in good diastereoselectivity (up to 95:5) and enantioselectivities up to 91%. The reaction with heteroaromatic aldehydes was also investigated leading to the corresponding 1,3 diols, in some cases with excellent stereoselectivities.

show abstract

Novel Chiral Biheteroaromatic Diphosphine Oxides for Lewis Base Activation of Lewis Acids in Enantioselective Allylation and Epoxide Opening

Cited by 54 publications

References 22 publications

Organocatalytic Stereoselective Direct Aldol Reaction of Trifluoroethyl Thioesters

Organocatalytic Stereoselective Direct Aldol Reaction of Trifluoroethyl Thioesters

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

Enantiomerically Pure Bithiophene Diphosphine Oxides as Catalysts for Direct Double Aldol Reactions

Contact Info

Product

Resources

About