Renata G. Lara

Addition of thiols to phenylselenoalkynes using KF/Alumina under solvent-free conditions

We present herein the results of a simple and efficient protocol for the hydrothiolation of phenylselenoalkynes promoted by KF/Al2O3 using solvent-free conditions. This improved method furnishes selectively the corresponding (Z)-1-phenylseleno-2-organylthio-1-alkenes in reasonable to good yields starting from selenoalkynes and aliphatic or aromatic thiols. The presence of the phenylselenium group in the alkyne directed the regiochemistry of the thiol addition. The catalytic system can be reused up to 4 times without previous treatment.

Glycerol as a promoting and recyclable medium for catalyst-free synthesis of linear thioethers: new antioxidants from eugenol

We describe herein the use of glycerol as an efficient and recyclable solvent for the addition of thiols to nonactivated alkenes. The catalyst-free reactions take place easily using glycerol at room temperature or heating and the corresponding linear thioethers were obtained in good to excellent yields. The method was used to synthesize new sulfur-containing eugenols, which were tested for their antioxidant activities. The semisynthetic thio-derivatives were more effective in inhibition of induced lipid peroxidation compared to the precursor eugenol and the synthetic antioxidant butylated hydroxyanisole.

Synthesis of Thiol Esters by the Reaction of Ricinoleic Acid with Thiols Under Solvent-Free Conditions

Abstract The synthesis of several ricinoleic acid thiol esters starting from cis-(R)-12-hydroxyoctadec-9-enoic acid and thiols in the presence of N,N′-dicyclohexylcarbodiimide (DCC) is described. The method is efficient for aromatic and aliphatic thiols, selectively affording the respective fat acid thiol esters in good yields under mild, neutral, and solvent-free conditions. The protocol is general and was extended to other carboxylic acids, furnishing the desired products in satisfactory yields. The (R,Z)-12-hydroxy-octadec-9-enylic acid benzylthiol ester 3a was successfully reduced to (R,Z)-12-hydroxyoctadec-9-enal 4.

Selective Synthesis of (Z)-Chalcogenoenynes and (Z,Z)-1,4-bis-Chalcogenbuta-1,3-dienes Using PEG-400

We present here our results on the temperature controlled, selective hydrochalcogenation of 1,4-diorganyl-1,3-butadiynes with nucleophilic species of selenium, tellurium and sulfur generated in situ from the respective diaryl dichalcogenide and NaBH4. Using polyethylene glycol (PEG)-400 at 30 oC the (Z)-chalcogenoenynes are obtained and at 90 oC the (Z,Z)-bis-chalcogen-1,3-butadienes are produced in good to excellent yields. Alternatively to conventional oil bath heating, the use of microwave irradiation is also presented as an alternative energy source that provides the expected products in few minutes.