Thiophenol Derivatives

With hydrogen sulfide at 500—600°C, monochlorotoluenes form the corresponding thiophenol derivatives (30). In the presence of palladium catalysts and carbon monoxide, monochlorotoluenes undergo carbonylation at 150—300°C and 0.1—20 MPa (1—200 atm) to give carboxyHc acids (31). Oxidative coupling of -chlorotoluene to form 4,4 -dimethylbiphenyl can be achieved in the presence of an organonickel catalyst, generated in situ, and zinc in dipolar aprotic solvents such as dimethyl acetamide (32,33). An example is shown in equation 4. 

An S4 coordination sphere of the type seen in the Ada protein, where four cysteines coordinate, was achieved with the tridentate tris(2-mercapto-l-phenylimidazolyl)hydroborato ligand. The zinc thiophenolate derivative showed reactivity of the thiolate linkage (Figure 8).506... 

Among the out-of-register mercaptans, derivatives (115) and (116) are equivalent in potency to their in-register counterparts (90) and (91), but with a reversal in stereoselectivity as indicated by the modest preference for the L-Leu analogue stereoisomer in subsite Pj. The thiophenol derivative (118) is very potent, at least in the presence of y9-mercaptoethanol which presumably suppresses disulphide formation. 

Saczewski and Debowski reported a l-thia-3-oxa-4-aza-Cope rearrangement of the adduct 163 formed when the A-aryl-Af-(4,5-dihydro-177-imidazol-2-yl)-hydroxylamine 162 reacted with carbon disulfide in the presence of triethylamine at room temperature (equation 48). The intermediate 164 formed after the [3,3] rearrangement lost a fragment and after successive or simultaneous rearomatization afforded a thiophenol derivative that provided 165. 

NMR spectral behavior of compounds 553 and 554 at low and room temperature means that, with kinetically more stable chelate catecholate ligands, the Sn—O bonds do not rupture. A mechanism which accounts for the coalescence of hexacoordinated stannaindane derivatives 553 and 554 (as well as the thiophenolate derivative 552) involves intramolecular N — Sn dissociation with a following enantiomerization by a Berry pseudorotation for pentacoordinated species1226 (equation 87). 

Thiophenols and thiophenol derivatives chemisorbed on well-defined electrode surfaces have also been studied by HREELS. The cyclic voltammetric peaks for the quinone/hydroquinone redox reaction of the 2,5-dihydroxythiophenol immobilized on the Pt surface was much broader than for the unadsorbed species the broadening vanished when a methylene group was placed between the—SH group and the phenyl ring. These results indicated strong substrate mediated adsorbate-adsorbate interactions. Such... 

The centers to be coupled may successfully be pre-fixed whenever sterically much less strained bicycles of type 48 (see Scheme 11) are synthesized 60,61). The protected thiophenol derivative 46 was derived from a-ionone by 21 steps. Release of the highly nucleophilic sulfur leads to the favored 12-membered ring. Oxidation to the sulfoxide augments the CH acidity and thus permits the desired ring contraction. 

The electrochemical reversibility of the M(VI)/M(V) couple for the complexes with sterically hindered ligands contrasts with the reported behavior of the [MoO(SPh)4] complex, which exhibited electrochemical irreversibility for the Mo(V)/Mo(VI) step but a reversible Mo(IV)/ Mo(V) couple. The sterically hindered aromatic substituent groups stabilize the molybdenum(VI) complex and decrease relative to the thiophenol derivative. The molybdenum(VI) species can also be isolated by chemical oxidation. [MoO(PFTP)4] was prepared by chemical redu-tion of [MoO(PFTP)4] . The presence of the electron-withdrawing substituents on the aromatic thiolate increases E ei relative to the thio-phenolate derivative. Evidently the properties of these last complexes are influenced primarily by the electron-withdrawing characteristics of the fluorine substituents rather than by steric factors (33). 

With respect to sulfiir-based nucleophiles, a rapid and efficient method for opening various epoxides with thiophenol derivatives was reported using solvent-free conditions and (C4Hi2N2)2[BiCl6]Cl H20 as a catalyst (13T11174). Also, a one-pot tandem synthesis of P-trimethylsilyloxy thioes-ters was reported by reacting epoxides with thioacids under solvent-free silica gel conditions (13SC1759). 

The question of regioselectivity remains, but as formula 489 indicates this can, in the majority of cases, be circumvented by choosing thiophenol derivatives as starting materials. 

A solid-phase synthetic route for the quinoxalines, which proceeds via benzyne intermediate, has been reported by Dixon et al. [37]. N-Alloc-3-amino-3-(2,4-difluoro-5-nitrophenyl)propanoic acid was tethered to Rink resin via its carboxylic acid group (Scheme 15). The 4-arylfluorine was displaced with a primary amine, alcohol, or thiol to create, respectively, a resin-bound aniline, phenol, or thiophenol derivative with one diversity element and one single atom (e.g., N, S, or O) diversity point. 

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