Asymmetric oxidation of some 1,3-dithianes in presence of chiral titanium complexes

Samuel, O.; Ronan, Baptiste; Kagan, Henri B.

doi:10.1016/0022-328x(89)87273-0

Cited by 39 publications

(14 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This continued interest has resided in the quest for new chiral auxiliaries. Using the Kagan system, Page et al confirmed the beneficial role of a carbonyl moiety (acyl or ester) at the 2-position [47] in order to obtain high diastereo-and enantiomeric excesses (up to 99%) on 2-substituted 1,3-dithiane 1,3-dioxides. Modena et al showed that higher diastereoand enantioselectivities were obtained on 1,3-dithiolane derivatives than on 1,3-dithiane and 1,3-oxathiolane.…”

Section: Metal-catalyzed Oxidationsmentioning

confidence: 99%

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Delouvrié¹,

Fensterbank²,

Nájera³

et al. 2003

ChemInform

View full text Add to dashboard Cite

show abstract

Section: Metal-catalyzed Oxidationsmentioning

confidence: 99%

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Delouvrié¹,

Fensterbank²,

Nájera³

et al. 2003

ChemInform

View full text Add to dashboard Cite

show abstract

“…From this point of view it is interesting to note that in the oxidation of 1c Cp 2 TiCl 2 /MS is superior to Mo(VI) catalyst and behaves similarly to VO(acac) 2 . 13a According to the literature, 14,15 the oxidation of 2-carbonyl dithianes proceeds with low trans stereoselectivities: for example, in the oxidation of 1d, a diastereomeric ratio of 75:25 was reported using the Modena 13a catalyst, whereas an almost completely stereospecific trans oxidation resulted on 1a and 1b 15 The reason of the lower ste- reochemical ratio was attributed to the enolizability of H-2 in the 2-carbonyl dithiane oxides. The diastereomeric mixture may be obtained with high stereoselectivity but, then the Lewis acidic titanium might equilibrate the isomeric mixture.…”

Section: Methodsmentioning

confidence: 95%

“…The known 1:1 trans/cis mixture of monosulfoxide 2g 14,18 was obtained by Ti(i-PrO) 4 -catalyzed oxidation of commercially available 1,3-dithiane 1g. The reduction of 2g by DIBAL-H or NaBH 4 , afforded a 1:1 mixture of the same compounds isolated after the titanocene oxidation of 1f, as confirmed by 1 H NMR analysis.…”

Section: Methodsmentioning

confidence: 99%

Titanocene Dichloride as a Convenient Catalyst for the Diastereoselective Oxidation of 2-Substituted 1,3-Dithianes and 1,3-Dithiolanes

Sala¹,

Labano²,

Lattanzi³

et al. 2002

Synthesis

View full text Add to dashboard Cite

Cp 2 TiCl 2 is an efficient catalyst for the diastereoselective mono-oxidation of 2-substituted 1,3-dithianes and 1,3-dithiolanes by tert-butyl hydroperoxide; comparable stereoselectivities and better yields than Ti(i-PrO) 4 were obtained. Activities are similar, provided activated 4Å molecular sieves are present in the titanocenepromoted process. Furthermore, Cp 2 TiCl 2 is a more moisture stable compound than Ti(i-PrO) 4 and therefore can be used in catalytic amounts of 1 mol%.The d 0 transition metal/alkyl hydroperoxide system has been extensively used for the oxidation of a number of organic compounds, in particular alkenes and thioethers. 1 In several instances, fairly good diastereoselectivities can be obtained in the oxidation of allylic alcohols 2 and thioethers 3 containing a stereogenic center. The level of the stereoselectivity, however, is dependent on the metal catalyst and the substrate structure.Ti(IV) alkoxides are commonly employed as catalysts in the diastereo-2b,4 and enantioselective 5 epoxidation of allylic alcohols as well as in the enantioselective oxidation of thioethers. 6 Surprisingly, cyclopentadienyl Ti(IV) compounds, despite their great availability and wide employment as catalysts in many homogeneous processes, 7 have been scarcely used in these oxidation reactions. 8 We have recently shown the applicability of titanocenes such as Cp 2 TiCl 2 , CpTiCl 3 and bis(cyclopentadienyl)titanium (IV) bis(trifluoromethanesulfonate) [Cp 2 Ti(OTf) 2 ] in the diastereoselective epoxidation of allylic 9 and bishomoallylic 10 alcohols and in the enantioselective sulfoxidation 11 using tert-butyl hydroperoxide (TBHP) as oxidant; the catalytic activity is markedly enhanced in the presence of activated 4Å molecular sieves.As an extension of our work, we became interested in the diastereoselective oxidation of dithianes. A great deal of data is avalaible in the literature on the oxidation of racemic 2-substituted 1,3-dithianes and 1,3-dithiolanes as models of cyclic thioethers. Except for enzymatic reactions, 12 d 0 transition metal/alkyl hydroperoxides proved to be the most stereoselective oxidizing systems for this type of substrates. 13 However, the chiral Kagan and Modena catalyst, a Ti(i-PrO) 4 /(+)-diethyl tartrate [(+)-DET] modified system, 13a,b,14,15 has been mostly used in stoichiometric amount to achieve a diastereo-and enantioselective process. The diastereoselectivity is merely associated with facial discrimination, whereas the enantioselectivity is a result of both facial selectivity and selection between the two enantiotopic sulfur atoms. In order to perform a diastereoselective transformation, a simple achiral transition-metal catalyst can be employed.Very few systematic reports 16 have appeared concerning the use of an achiral reagent for the diastereoselective oxidation of thioethers. Indeed, a catalytic (using minimal amount of catalyst) process would be highly desiderable and the use of cheap, safe and stable catalysts should be highly preferable.In the present work, we compare s...

show abstract

“…Modena et al showed that higher diastereo‐ and enantioselectivities were obtained on 1,3‐dithiolane derivatives than on 1,3‐dithiane and 1,3‐oxathiolane 46. Taking advantage of the optimization of his oxidation method, notably by replacing the tert ‐butyl hydroxyperoxide by the cumyl hydroperoxide, Kagan et al reported the asymmetric oxidation of 2‐substituted 1,3‐dithianes with ee s up to 80% 47,48. Kagan et al also proposed a general model for predicting the absolute configuration: the (+)‐tartrate gives birth to the sulfoxide B from A (Scheme ).…”

Section: Preparation Of C2‐symmetric Bis(sulfoxides)mentioning

confidence: 99%

“…These seminal works paved the way for the preparation of various enantioenriched mono‐ and dioxides of dithioacetals. Using the Kagan system, Page et al confirmed the beneficial role of a carbonyl moiety (acyl or ester) at the 2‐position47 in order to obtain high diastereo‐ and enantiomeric excesses (up to 99%) on 2‐substituted 1,3‐dithiane 1,3‐dioxides 49,50. In some cases, a small degree of over‐oxidation furnished the C 2 ‐symmetric disulfoxide.…”

Section: Preparation Of C2‐symmetric Bis(sulfoxides)mentioning

confidence: 99%

The Chemistry of C2-Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

et al. 2002

View full text Add to dashboard Cite

Keywords: Asymmetric synthesis / Chiral acyl anions / Ligand design / Bis(sulfoxides)The preparation of various racemic or enantiopure C 2 -symmetric bis(sulfoxides) has been developed over the last decades. Numerous applications in organic synthesis (anionic condensation, cycloadditions) as well as in coordination chemistry have been worked out.[a] Université P. et M. Curie, UMR 7611, MICROREVIEWS: This feature introduces the readers to the authors' research through a concise overview of the selected topic. Reference to important work from others in the field is included.

show abstract

Asymmetric oxidation of some 1,3-dithianes in presence of chiral titanium complexes

Cited by 39 publications

References 16 publications

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Titanocene Dichloride as a Convenient Catalyst for the Diastereoselective Oxidation of 2-Substituted 1,3-Dithianes and 1,3-Dithiolanes

The Chemistry of C2-Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Contact Info

Product

Resources

About

Asymmetric oxidation of some 1,3-dithianes in presence of chiral titanium complexes

Cited by 39 publications

References 16 publications

The Chemistry of C2‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

The Chemistry of C2‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Titanocene Dichloride as a Convenient Catalyst for the Diastereoselective Oxidation of 2-Substituted 1,3-Dithianes and 1,3-Dithiolanes

The Chemistry of C2-Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

Contact Info

Product

Resources

About

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis

The Chemistry of C₂‐Symmetric Bis(sulfoxides): A New Approach in Asymmetric Synthesis