Menthyl P-toluenesulfinate Research Articles

An Improvement of the Synthesis of (1R,2S,5R)-(–)-Menthyl (S)-p-Toluenesulfinate

The preparation of menthyl p-toluenesulfinate has been reported using different procedures described in this spotlight highlighting the procedure of Solladie as the most convenient and efficient. A number of fundamental modifications of the Solladie's reaction conditions are described in this spotlight allowing the most cost-efficient preparation of a tens-of-gram of enantiopure menthyl p-toluenesulfinate in one day without significant by-product formation, with an excellent yield of 72% and a d.r. > 98:2.

Single‐Step Preparation of a 4‐(Dimethylamino)pyridine Analogue Bearing a Sulfoxide as New Chiral Inducer. Preliminary Evaluation as Nucleophilic Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Single-Step Preparation of a 4-(Dimethylamino)pyridine Analogue Bearing a Sulfoxide as New Chiral Inducer. Preliminary Evaluation as Nucleophilic Catalyst

A one-step synthesis of a new chiral DMAP-la equivalent is reported by bromine-magnesium exchange reaction of the 3-bromo-4-(dimethylamino)pyridine (2). The chiral sulfoxide appendage is introduced by trapping the resulting Grignard intermediate with (1R,2S,5R)-(-)-(S)-menthyl p-toluenesulfinate affording (S)-1a in 60% yield and high optical purity. A preliminary evaluation of la as nucleophilic catalyst has demonstrated promising selectivity (s = 4.5) during acylative kinetic resolution of various alcohols.

Lithium—Sulfoxide—Lithium Exchange for the Asymmetric Synthesis of Atropisomers under Thermodynamic Control.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Lithium-sulfoxide-lithium exchange for the asymmetric synthesis of atropisomers under thermodynamic control.

Ortholithiation and reaction with (-)-menthyl p-toluenesulfinate introduces a sulfoxide substituent ortho to the stereogenic Ar-CO axis of an aromatic amide. The sulfoxide exerts a powerful conformational bias on the axis, such that after rapid equilibration at ambient temperature essentially only one of two diastereoisomeric Ar-CO atropisomers is populated. Sulfoxide-lithium exchange by treatment with t-BuLi regenerates the ortholithiated amide in an enantiomerically pure and conformationally stable form. Rapid electrophilic trapping of the organolithium therefore generates highly enantiomerically enriched atropisomeric tertiary aromatic amides. The overall process, involving temporary substitution of lithium to sulfoxide to lithium, amounts to a dynamic resolution under thermodynamic control.

Stereoselective Synthesis of Racemic and Optically ActiveE-Vinyl andE-Dienyl Sulfoxides via Wittig Reaction of α-Sulfinyl Phosphonium Ylides

A series of α-sulfinyl phosphonium ylides have been obtained in the reaction of phosphonium mono- and diylides with sulfinic acid esters. The use of (−)-(S)-menthyl p-toluenesulfinate in this reaction afforded the corresponding (S)-((p-tolylsulfinyl)methyl)triphenylphosphonium ylide. The Wittig reaction of these ylides with saturated and unsaturated aldehydes resulted in the formation of racemic and optically active (+)-(R)-vinyl and dienyl sulfoxides with the E-geometry. The synthesis of (+)-(R)-((p-tolylsulfinyl)methyl)triphenylphosphonium iodide as a precursor of the optically active ylide has also been described.

Synthesis of enantiomerically pure acyclic α-sulfinyl ketimines

Two different methods to obtain enantiomerically pure N-alkyl and N-aryl α-sulfinyl ketimines are reported. Reaction of enantiomerically pure α-sulfinyl ketones ( 1– 6) with benzylamine or p-methoxyaniline, in the presence of molecular sieves (3 Å), yields the corresponding of N-benzyl and N- p-methoxyphenyl ketimines ( 7A– 12A and 7B– 12B). Better results were achieved by α-sulfinylation of ketimines ( 13A– 18A and 13B– 18B) with (−)-menthyl p-toluenesulfinate in the presence of lithium ( N-arylimines) or magnesium ( N-benzylimines) bases. The different tautomeric behaviour of the obtained N-aryl and N-alkyl derivatives is reported.

Apparent Molar Volume and Viscosity of Compounds with Asymmetric Carbon Atoms

Apparent molar volumes and viscosities of l- and meso-tartaric acid in water and of (1R,2S,5R)- and (1S,2R,5S)-menthyl p-toluenesulfinate in 1-butanol at 25 °C are reported. The differences observed between l- and meso-forms of tartaric acid and between (1R,2S,5R)- and (1S,2R,5S)-forms of menthyl p-toluenesulfinates are interpreted in terms of structural differences arising from different configurations of isomeric compounds. The results support the conclusion that different forms of compounds with more than one asymmetric center show differences in solution behavior.

Benzyl Methyl (S)-2-(p-Tolylsulfinyl)maleate, an Efficient Dienophile in Asymmetric Diels-Alder Reactions

The enantiomerically pure dienophile (3) [1-benzyl 4-methyl (S)-(p-to- lylsulfinyl)maleate] was readily prepared in a three-step sequence from benzyl acetate and (-)-(S)-menthyl p-toluenesulfinate (46% overall yie- ld). This vinyl sulfoxide reacted in high yields and with very high re- gioselectivities and stereoselectivities with a wide variety of 1,3-di- enes (10 examples) at low temperature in the presence of Eu(fod) 3 or TiCl 4 . Whereas cycloadditions catalyzed by TiCl 4 (usually carried out at -78 o C) occurred with complete regioselectivity, endo selectivity, and π-facial selectivity, the cycloaddition catalyzed by Eu(fod) 3 (usu- ally performed at 0 o C) also occurred with very high regioselectivity and π-facial selectivity, but with low endo selectivity. Interestingly, all the adducts (excepting the adducts from cycloentadiene) are unstable at room temperature, undergoi,g spontaneous sulfinyl elimination to give 1,3-cyclohexadienes (7) and/or 1,4-cyclohexadienes (11), in excel- lent yields

Asymmetric synthesis of β-amino-γ-hydroxysulfoxides

Optically pure [4-(3′-oxazoline)]methyl methyl- and p-tolylsulfoxides ( 5R, 5S, 6R and 6S) were prepared from the enolate of the 3-oxazoline 4 and the corresponding o.p. diacetone-D-glucofuranosyl methanesulfinate and menthyl p-toluenesulfinate. The highly diastereoselective reduction of these substrates was successfully achieved using DIBAL/ZnCl 2 at −78°C. In this way, four o.p. N-cyclohexyl-β-amino-γ-hydroxysulfoxides, chiral key intermediates in the asymmetric synthesis of various biologically active molecules, were obtained.

Asymmetric synthesis of both enantiomers of methyl and t-butyl 3-hydroxybutyrates monitored by optically active sulfoxides.

Methyl and t-butyl (R) and (S) 3-hydroxybutyrates were prepared by stereoselective reduction of (R) 4-[p-tolylsulfinyl]-3-oxobutyrate, readily available in one step from (−)(S) menthyl p-toluene sulfinate.

Synthesis and Diels-Alder reactions of homochiral 2-sulfinylmaleates with cyclopentadiene

Enantiomerically pure 2-p-tolylsulfinylmaleates 1, 2 and 3 have been readily prepared by Knoevenagel reaction between (S)-menthyl p-toluenesulfinate and glyoxylic acid. Their asymmetric Diels-Alder reactions with cyclopentadiene have been studied under a wide range of uncatalyzed and catalyzed conditions and the stereochemical results have been explained by assuming a steric control approach, in term of S- cis or S- trans favoured conformations. Uncatalyzed Diels-Alder reactions of 1 and some Lewis acid catalyzed Diels-Alder reactions of 2 show high facial and endo selectivities. The facial selectivity of dienophile 2 highly depends on the Lewis acid, whereas reactivity of 1 and 3 is very sensitive to the solvent. These sulfinylmaleates 1, 2 and 3 act as synthetic equivalents of chiral acetylenedicarboxylates in Diels-Alder reactions after basic elimination of the sulfinylic moiety in the resulting adducts.

α-PHOSPHORYL SULFOXIDES 7.1CHIROPTICAL PROPERTIES OF α-PHOSPHORYL SULFOXIDES

Abstract The paper describes the synthesis and chiroptical properties of (+)-α-phosphoryl sulfoxides of general formulae, R1 2P(X)CHR2S(O)Tol-p (where R1=MeO, EtO. Ph, Me2N, X=O,S, R2=H,Me, Cl) obtained from (-)-(S)-menthyl p-toluenesulfinate and the corresponding α-phosphonate, α-thiophosphonate and α-phosphinoxide anions. The CD curves of (+)-α-phosphoryl sulfoxides are of the same shape with two Cotton effects of opposite sign. At 240–245 nm one observes the positive Cotton effect while that at 220 nm is negative. The CD spectra of all (+)-α-phosphoryl sulfoxides measured are almost identical with that of (+)-(R)-methyl p-tolyl sulfoxide indicating that they have the S-chirality at sulfur. The change of ethanol for isooctane as a solvent does not influence the UV and CD spectra.

ChemInform Abstract: A SIMPLE PREPARATIVE METHOD FOR OPTICALLY PURE 1‐ALKENYL P‐TOLYL SULFOXIDES VIA 1‐ALKYNYL P‐TOLYL SULFOXIDES

AbstractDie optisch reinen Alkinylsulfoxide (III), hergestellt aus den Grignard‐Verbindungen (I) und dem Sulfinat (II), werden stereoselektiv in die E‐Alkenylsulfoxide (IV) übergeführt.

A SIMPLE PREPARATIVE METHOD FOR OPTICALLY PURE 1-ALKENYL p-TOLYL SULFOXIDES VIA 1-ALKYNYL p-TOLYL SULFOXIDES

Abstract 1-Alkynyl Grignard reagents react with (SS)-(−)-menthyl p-toluenesulfinate in toluene to give optically active 1-alkynyl p-tolyl sulfoxides in high yields. The 1-alkynyl sulfoxides thus obtained undergo a stereoselective hydroalumination followed by hydrolysis to afford the corresponding (E)-1-alkenyl p-tolyl sulfoxides with high optical purity.

Ethyl-(r)-(4-methylphenylsulfinyl)-n-methoxy acetimidate a useful chiral acetate equivalent in aldol type condensations

Ethyl N-methoxyacetimidate was metallated by lithium amides and reacted with (-)-(S)-menthyl p-toluenesulfinate to afford, in excellent yield, (R) - (4-methylphenylsulfinyl)-ethyl-N-methoxy acetimidate (2). Compound (2) was tested in aldol-type condensations with various aldehydes, and the adducts, after desulfurization, were converted into optically active β-hydroxyesters with good ⩾80%) e.e. The stereochemical outcome of the reaction of benzaldehyde was found to be dramatically affected by changing either the counterion of the enolate from lithium to zirconium or by going from kinetic to thermodynamic control.