Thietanes metal complexes

Only a limited number of examples are known of applications of thietanes in organic synthesis. Prominent among these examples would be electrophilic ring opening reactions leading to polyfunctional sulfur compounds (33)-(37), utilization of 3-thietanones (55) and metal complexes (87) derived therefrom as oxyallyl zwitterion equivalents in cycloaddition reactions, synthesis of dipeptide (63) with a /3-thiolactone, Raney nickel desulfurization of thietanes (e.g. 120 cf. Table 7) as a route to gem-dimethyl compounds, and desulfurization of thietanes (e.g. 17) in the synthesis of cyclopropanes (also see Table 7). 

Aromatic organosulfur compounds such as thiophenes, benzothiophenes and dibenzothiophenes are frequently contained in fossil oil and their sulfur atoms are generally difficult to remove in HDS process [106], In the industrial HDS process, Mo/Co/S or Ni/Mo/S heterogeneous catalysts supported on alumina are widely employed. In order to obtain ideas to develop more efficient catalysts as well as to shed some light on their mechanisms at a molecular level, transition metal complex-mediated cleavages of C-S bond are extensively studied. On the other hand, thiiranes and thietanes are frequently employed for preparation of transition metal sulfides, in which their C-S bonds are smoothly cleaved. In this section, the C-S bond cleavages of thiophene derivatives, thiiranes, thietanes, vinylic sulfides, allylic sulfides, thiols and dithioacetals are overviewed. 

Although the C-S bond of thiiranes is cleaved by both acids and bases [129], such bond cleavage reactions by transition metal complexes have been extensively studied from both mechanistic and synthetic points of view. For example, oxidative addition of thiiranes or thietane to NiEt2(bpy) (Eq. 3.33) or Ni(cod)(bpy) (Scheme 3.66) gives thianickellacycle complex [130]. Exposure of the thianickellacyclopentane to the atmospheric CO gives y-thiobutyrolactone. 

The catalysed macrocyclization of thietanes by metal carbonyl complexes has been reviewed <00ACR171>. Electronically stabilized thiones have been shown to undergo [2+2] cycloaddition with benzyne to give 27/-benzo[i>]thietes, for example 6 <00BCJ155>. 

In several cases thietane derivatives have been used as ligands in organo-metallic compounds. Stable enolate complexes have been derived from tetra-methyl-3-thietanone and diiron nonacarbonyl. Both compounds were heated in n-hexane at 60°C in an argon atmosphere for longer periods of... 

The treatment of cyclopentadienyI-metal-2-alkenyl carbonyl complexes, such as 274 and 275, with SO2 leads to the formation of thietane 1,1-dioxide as ligand (Eqs. 73 and 74). Thietane and platinum(II) have also been found... 

The block copolymer of ethylene oxide and 3,3-dimethylthietane shows useful properties of complexing halogen and heavy metal salts (79MI51402). Thietanes can be polymerized with methylmagnesium iodide as well as with a variety of electrophiles such as methyl sulfate, trimethyloxonium tetrafluoroborate, triethylaluminum, boron trifluoride and phosphorus trifluoride (67IC1461, 67MI51400). Thietane (210) has been patented as a stabilizer for poly(vinyl chloride) (73USP3767615). 

The reaction of the thio- and selenoaldehyde complexes with vinyl ethers provides metal-coordinated substituted thietanes and selenetanes.224,250-252 The cycloadditions are highly regio- and stereoselective. 

Platinum and palladium complexes of thietane and 3,3-dimethylthietane have been prepared as illustrated for 90. The platinum complexes exist in cis and trans configurations, but no cis-trans isomerization of the palladium complexes in the solid state was observed. Stability constants of thietane with Mn(ll), Co(II), and Ni(II) chelates have been determined. Proton nmr studies show that the absorption of the a-methylene protons, which are syn to the metal, is shifted downfield (about 0.7 ppm) more than the absorption of the protons anti to the metal (about 0.4 ppm downfield). Energies of activation for pyramidal inversion were determined. Bis-ruthenium complexes of di-, tri- and tetraspirothietanes (e.g., 90a) show rapid electron transfer between the ruthenium ions long-range electron tunneling was proposed. ... 

More recently, metal-induced cyclo-oligomerization reactions of thietane using transition metal carbonyl complexes such as [Re3(CO)10(/i-SCH2CH2CH2)(/i-H)3] have been shown to yield [12]aneS3, [16]aneS4, and [24]aneS6, albeit not yet in synthetically useful quantities.25,26... 

Catalytic macrocyclizations of thietanes by metal carbonyl complexes 00ACR171. 

R. D. Adams, in Catalysis by Di- and Polynuclear Metal Cluster Complexes Catalytic Macro-cyclization of Thietanes (Eds. R. D. Adams, F. A. Cotton), Wiley-VCH, New-York, 1998, pp. 283. 

B7.1 Nucleophilic ring-opening transformations of bridging thietane ligands in metal carbonyl cluster complexes B7.2 Chemistry of thietane ligands in polynuclear metal carbonyl complexes... 

Metal carbonyl complexes show rich reactivities toward thiiranes and thietanes [134]. Reaction of W(CO)5(NCMe) with thiirane results in the ligand exchange reaction to give W(thiirane)(CO)5 (Scheme 3.70) [135]. This complex catalyzes formation of cyclic polydisulfides with olefin elimination (Scheme 3.71). 

Similary, thietane also displaces the coordinated acetonitrile on the electron poor metal center in Os3(CO)n(NCMe) to give Os3(CO)n[S(CH2)3] (Scheme 3.72) [136,137]. Photo-irradiation of the resulting complex leads to... 

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