Tetrahydrothiophenes functionalized

A series of functionalized tetrahydrothiophenes has been prepared by acid induced organocatalytic reactions involving a,p-unsaturated aldehydes and 2-mercapto-l-phenylethanone 24. This procedure led to good yields of products displaying useful enantiomeric excess, as illustrated by construction of the target 25 in the presence of the catalyst 26 <06JA14986>. 

SCHEME 1.10 Qrganocatalytic asymmetric synthesis of functionalized tetrahydrothiophenes [35]. 

Thiophene is the typical model compound, which has been extensively studied for typifying gasoline HDS. Although, some results are not completely understood, a reaction network has been proposed by Van Parijs and Froment, to explain their own results, which were obtained in a comprehensive set of conditions. In this network, thiophene is hydrodesulfurized to give a mixture of -butenes, followed by further hydrogenation to butane. On the considered reaction conditions, tetrahydrothiophene and butadiene were not observed [43], The consistency between the functional forms of the rate equations for the HDS of benzothiophene and thiophene, based on the dissociative adsorption of hydrogen, were identical [43,44], suggesting equivalent mechanisms. 

Tetrahydrothiophene functions as a catalyst in an annulation reaction leading to chromenes. It is postulated that a sulfonium ylide is formed initially which then adds intramolecularly to an acrylate <2006OL3853>. 

Symmetrical sulfides are obtained in 70-90% yields by refluxing aqueous alcoholic solutions of halides with sodium sulfide. The nonahydrate of sodiiun sulfide is a satisfactory reagent for the reac-tion. Tetramethylene and pentamethylene halides give cyclic sulfides, e.g., tetramethylene sulfide (tetrahydrothiophene) (64%). Halides containing several other important functional groups have been employed. Typical examples include methallyl chloride, and halides with hydroxyl, ethoxyl, carboxyl, and diethylamino groups in the beta position. A dry synthesis of phenyl sulfide from calcium oxide, sulfur, and chlorobenzene at 300° has been reported. ... 

E. coli, under anaerobic conditions, when nitrate is the electron acceptor, Q is the preferred quinone. But in the absence of MK can substitute for this function. However, under anaerobic conditions when fumarate, trimethylamine A -oxide (TMAO), dimethylsulfoxide (DMSO), or tetrahydrothiophene 1-oxide (THTO) serve as the electron acceptors, the presence of MK is obligatoryReconstitution studies using membrane preparations from quinone-deficient strains suggest that MK is specifically involved in fumarate and DMSO reduction, while either MK or DMK can function in TMAO reduction, and that nitrate reduction requires either Q or MK. ... 

Given the following values of the rate constants, prepare plots of the dimensionless concentrations of thiophene, tetrahydrothiophene, butene, and butane as functions of time for a period corresponding to 50% reaction of the initial thiophene ... 

The TIPS variant in eq 1 is used not only neat on the cyclic C-H substrates THF, tetrahydrothiophene, and cyclohexane, but also in acetonitrile with adamantane, which substituted exclusively at the tertiary C-H (50% yield). Alkynylation was also successful with distal functionality, i.e. R = (CH2)20SiR3 and (CH2)3C1, but the triflone could not be formed with ether functionality closer to the acetylene. 

Most tosylhydrazone sodium salts could be usually isolated from the reaction of the corresponding tosylhydrazones with sodium methoxide. However, a number of more functionalized hydrazone sodium salts, such as those derived from alkenyl aryl sulfonylhydrazones, ketone sulfonylhydrazones, and trimethylsi-lylacrolein sulfonylhydrazones, could not be isolated and an in situ salt generation procedure using NaHMDS was developed. A mixture of the desired hydrazones and NaHMDS was stirred at —78 °C then concentrated down before the addition of rhodium acetate, tetrahydrothiophene, BnEtsNCl, and the aldehyde to produce the required epoxide in high yields (eq 29). 

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