Bifunctional thiols

Hyun et al. [345] prepared PbS Q-dots in a suspension and tethered them to Ti02 nanoparticles with a bifunctional thiol-carboxyl linker molecule. Strong size dependence due to quantum confinement was inferred from cyclic voltammetry measurements, for the electron affinity and ionization potential of the attached Q-dots. On the basis of the measured energy levels, the authors claimed that pho-toexcited electrons should transfer efficiently from PbS into T1O2 only for dot diameters below 4.3 nm. Continuous-wave fluorescence spectra and fluorescence transients of the PbS/Ti02 assembly were consistent with electron transfer from small Q-dots. The measured charge transfer time was surprisingly slow ( 100 ns). Implications of this fact for future photovoltaics were discussed, while initial results from as-fabricated sensitized solar cells were presented. 

In the anodic process of another bifunctional thiol, 1,3-propanedithiol, all three forms - a neutral molecule, its mono-, and dianion undergo oxidation. The addition of HO ions to the solution or a cathodic preelectrolysis (due to the reduction of protons), shift the equilibrium toward... 

A-Phenyltriazolinedione is an efficient and chemoselective reagent for the oxidation of thiols to their corresponding symmetrical disulfides. The method is applicable to aromatic, aliphatic, and bifunctional thiols and excellent yields are obtained. A two-step mechanism (Scheme 6) has been proposed.109... 

Bifunctional thiols react with dichlorosulfanes to give cyclic organic polysulfanes (Section 2.2.1). 

Such thin-film assembly is not limited to silica surfaces it has been extended to other surfaces, such as gold and germanium (231). Film construction is initiated by first depositing a bifunctional thiol on gold or amino silane on germanium surfaces such that a spacer consisting of phosphonic acid function is... 

Moustatih, A., and Garnier-Suillerot, A. (1989) Bifunctional antitumor compounds synthesis and characterization of a gold(III)-streptonigrin complex with thiol-modulating properties. Journal of Medicinal Chemistry, 32, 1426. 

Harris, W.E. and Stahl, W.L. (1980). Oiganisation of thiol groups of electric eel electric organ Na/K ion stimulated adenosine triphosphatase, studied with bifunctional reagents. Biochem. J. 185, 787-790. 

Develop bifunctional ligands which NCI, NIH have a high affinity for Pb(ll) and Bi(lll) systematic exploration of incorporating thiol donor groups into chelating agents... 

A development reported recently [519] involves reduction of the cystine disulphide bonds in wool with either thioglycolic acid or tetrakis(hydroxymethyl)phosphonium chloride to form thiol groups, followed by crosslinking with bifunctional reactive dyes. This gave improved insect resistance but had adverse effects on physical properties such as strength, shrinkage and stiffness, thus limiting the potential of the process for commercial use. 

Figure 28.17 FeBABE is a bifunctional chelating agent containing an EDTA group on one side and a thiol-reactive bromoacetyl group on the other end. The EDTA group is coordinated with an iron ion.

Immobilization of these clusters on Pt(hkl) surfaces, employing bifunctional linkers with one pyridyl- and one thiol-based anchoring group, was achieved [334, 335]. The terminal pyridyl anchor ensures a strong chemical bond to the... 

The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane, provides 9,ll-ethano-13,15-isoxazolinoprostanoids, PGH analogs, with alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (461). Chemical transformations of 9,11-ethano-13,15-isoxazolinoprostanoids furnish prostanoids with bifunctional fragments of P-hydroxyketone and a-aminoalcohol in the oo-chain. The reaction of P-hydroxy ketones with methanesulfonyl chloride gives rise to prostanoids with an enone component in the oo-chain. 9,ll-Ethano-16-thiaprostanoids have been prepared, for the first time, by nucleophilic addition of thiols to the polarized double bond in the oo-chain. The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane provides 9,ll-ethano-13,15-isoxazolinoprostanoids with an alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (462). 

The electrooxidation of thiophenol [19], 2-mercaptobenzothiazole [22], 6- and 2-thiopurine [23], 2-thiopyridine [24] results in their disulfide derivatives in good yields. Bifunctional compound, 2,6-purinedi-thiol [23] can form first a 6,6 -disulflde (4), and then, by subsequent oxidation of the latter, give a cyclic product with two S - S bridges (Scheme 5). 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

Wu, M. H. Jacobsen, E. N. (1998) Asymmetric ring opening of meso-epoxides with thiols enantiomeric enrichment using a bifunctional nucleophile., J. Org. Chem., 63 5252-5254. 

Nagao has disclosed bifunctional chiral sulfonamide 69 as being effective for the thiolytic ASD of meso-cyclic anhydrides in up to 98% ee when employed at the 5 mol% level for 20 h at room temperature in ether [228], Catalyst 69 is a 1,2-diamine derivative in which one of the nitrogens presents as an acidic NH group (part of an electron deficient aryl sulfonamide) and the other as a nucleophihc/basic teri-amine group with the intention to act synergistically in activation of the substrate carbonyl function and thiol nucleophile respectively (Fig. 16) [228],... 

Synthesis of dihydroartemisinin polyethylene-glycol dimers 130 may be achieved easily in one chemical operation starting with dihydroartemisinin 29a and the corresponding bifunctional alcohol or thiol under acidic conditions (Table 7) <1997BMC1257>. 

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