Liliana Marzorati

Asymmetric sulfoxidation of a β-carbonyl sulfide series by chloroperoxidase

Abstract The chloroperoxidase (CPO)-catalyzed oxidation of a series of β-carbonyl sulfides to sulfoxides has been studied at room temperature in aqueous citrate buffer. For dialkyl β-carbonyl sulfides, the products with methyl and ethyl substituents are obtained in ca. 100% yield. However when the alkyl group is n- propyl or i -propyl the yield drops dramatically (25%). An aryl sulfide derivative afforded product in very low yield (4%), but when the phenyl group bears a carbonyl, and the sulfur substituents are methyl or ethyl, the oxidation occurs with high yields (91–95%). Steric control of the sulfoxidation reaction is also confirmed with cyclohexanone derivatives, where a low product yield is observed even at high enzyme concentrations. Noteworthy are the yields obtained with cyclopentanone sulfide (65%) and an unexpected quantitative yield obtained with the γ-butyrolactone sulfide.

Catálise de transferência de fase

Since its discovery, phase transfer catalysis (PTC) has grown considerably and nowadays is one of the most versatile preparative methods. The search for new catalysts, their use in PTC asymmetric synthesis and the attempts to understand their mechanistic role are modern and exciting topics of investigation. A review on main achievements in the last two decades is presented.

Sulfenylation of β-keto sulfoxides. III. Diastereoselectivity induced by a chiral phase transfer catalyst

Abstract The asymmetric induction in the sulfenylation of several β-keto sulfoxides under phase transfer catalytic conditions in the presence of the chiral catalyst N-benzylquininium chloride was investigated. It is concluded that the diastereoselectivity is not accompanied by enantiomeric resolution.

Graft copolymers with immobilized peroxidase for organic synthesis

The graft copolymer poly(propylene)-graft-poly(acrylic acid) (PP-G-AA) was prepared by radiation-induced graft copolymerization of acrylic acid onto polypropylene spheres and characterized by thermal analysis and scanning electron microscopy (SEM). Maximum percentage of grafting (70%) was obtained at a total dose of 12 kGy using 30% (w/w) of acrylic acid. The Michaelis constant, KM, and the maximum reaction velocity, VMax, were determined for the free horseradish peroxidase and for the immobilized horseradish peroxidase. The enzyme affinity for the substrate (KM/Vmax) remains quite good after immobilization. The sulfoxidation reaction of a ketosulfide was investigated with the immobilized peroxidase.

α-Phosphoryl sulfoxides. XI. Sulfenylation of α-phosphoryl sulfoxides and a general synthesis of optically active ketene dithioacetal mono-S-oxides

Abstract Sulfenylation and selenenylation of α-phosphoryl sulfoxides 1 with S-methyl methanethiosulfonate and phenylselenenyl bromide, respectively, affording α-methylsulfenyl- and α-phenylselenenyl-α-phosphoryl sulfoxides 8 and 9 are described. Sulfenylation of (+)-(S)-dimethoxyphosphorylmethyl p-tolyl sulfoxide 2 gave a mixture of optically active diastereoisomers of the sulfoxide 8a which is a key substrate in the Horner-Wittig synthesis of enantiomeric ketene dithioacetal mono-S-oxides 10. The E Z ratio of geometrical isomers of 10 was determined and briefly discussed. The crystal and molecular structure of E-1-p-tolylsulfinyl-1-methylsulfenyl-2-phenyl-ethene 10a is reported.

Novel reaction: Decarboxylative Ramberg-Bäcklund rearrangement in some α-isopropyl sulfonyl carboxylic esters

The reaction of some isopropylsulfonyl α-mono and disubstituted esters with KOH/t-BuOH/CCl4 is reported For the α,α-dialkyl and α-monoaryl substituted derivatives the key step of this reaction is proposed to be the decarboxylative 1,3-displacement in the chlorinated intermediates.

SULFANYLATION REACTIONS OF CARBONYL COMPOUNDS AND CARBOXYLIC ACID DERIVATIVES EMPLOYING SULFUR ELECTROPfflLES. A REVIEW

1 . in situ Oxidation of Thiols or Thiolates ................................................................................. 450 2 . Electrochemical Generation of the Sulfanylating Agent ....................................................... 451 I1 . CATALYTIC METHODS ...................................................................................................... 451 III . monoversus bis-SULFANYLATION .................................................................................. 453 IV . REGIOAND CHEMOSELECTIVITY ............................................................................. 456 V . STEREOSELECTIVE SULFANYLATION REACTIONS .............................................. 458

New decarboxylation, de-ethoxycarbonylation and desulfonylation, followed by sulfenylation of some half-esters of malonic acids and α-sulfonylmalonic esters

The sulfenylation of some half-esters of malonic acids and some α-sulfonylmalonic esters with several sulfenylating reagents was investigated. Evidence was provided that in the case of the half-esters, in which NaH–dimethyl sulfoxide was employed, the formation of α,α-disulfenylated carboxylic esters may occur by two different reaction sequences, initiated either by dianion formation or decarboxylation. It is shown that, in the case of the α-sulfonylmalonic esters, in which diazabicyclooctane in refluxing toluene was employed, two competitive reactions may take place: de-ethoxycarbonylation or desulfonylation, both followed by sulfenylation.

Membrane morphology modifications induced by hydroquinones.

We synthesize and characterize alkylthiohydroquinones (ATHs) in order to investigate their interactions with lipid model membranes, POPE and POPC. We observe the formation of structures with different morphologies, or curvature of the lipid bilayer, depending on pH and increasing temperature. We attribute their formation to changes in the balance charge/polarity induced by the ATHs. Mixtures of ATHs with POPE at pH 4 form two cubic phases, P4(3)32 and Im3m, that reach a maximum lattice size at 40 °C while under basic conditions these phases only expand upon heating from room temperature. The cubic phases coexist with lamellar or hexagonal phases and are associated with inhomogeneous distribution of the ATH molecules over the lipid matrix. The zwitterionic POPC does not form cubic phases but instead shows lamellar structures with no clear influence of the 2,6-BATH.

PTC SULFANYLATION OF SOME CARBOXYLIC ACIDS DERIVATIVES ACTIVATed BY α-SULFONYL OR α-SULFINYL GROUP, In SOLID-LIQUID SYSTEM

Abstract The sulfanylation of α-sulfonyl substituted lactone and thioesters and α-sulfinyl-substituted esters and thioesters, employing solid K2CO3, S-methyl methanethiosulfonate and TEBA, is reported. The results are compared with those in the homogeneous phase and in the non-catalytic two-phase system.