Thiiranes complexes

Three-membered rings should in principle be accessible by reaction of heteroaldehyde and -ketone complexes with Q sources. This was verified by the synthesis of the thiirane complex 143 from thiobenzaldehyde complex 99a and diphenyl diazomethane [Eq. (30)]. The reaction was assumed to proceed via a 1,3,4-thiadiazolidine complex as the intermediate that loses dinitrogen to give 143.254... 

In a related reaction, the benzylidene complex (CO)sW=C(Ph)H reacted with several diaryl thioketones affording thiirane complexes 145506 (equation 155). 

Transition metal complexes catalyze desulfurization of thiiranes. Complexes of Rh <1986TL3573>, Re <1997TL7701, 1999CC1003>, and Mo <2003JA3871> have been successfully employed in catalytic quantities. The presence of a stoichiometric sulfur acceptor such as carbon monoxide or an alkene, phosphine, or arsine is required. In Re-catalyzed desulfurization, the formation of an intermediate Re =S species via initial coordination of the thiirene ligand has been suggested (Schemes 12 and 13) <1997TL7701>. Kinetics and mechanism of sulfur... 

A new easier approach to cyclic poly(aliphatic disulfide)s by catal3d ic transformation of thiiranes by (thiirane)W(CO)5 complexes has been studied (85,86). For this purpose, the new thiirane complexes such as W(CO)5(thiirane) (cl), W(CO)5(cis-dimethylthiirane) (c2), and W(CO)5(frans-dimethylthiirane) (c3) were prepared and characterized. It was found that cl, as W(CO)5(NCMe) (87) used earlier, transforms free thiirane (thiacyclopropane, ethylene sulfide) [420-12-2] (28) into a mixture of cyclic poly(disulfide)s (29), and ethylene, catalytically the compound (29a) was the major product ( 66%). Also, cis- and traras-dimethylthiirane were catalytically transformed hy c2 and c3 with the formation of small amounts of cyclic disulfides. The mechanism of these reactions has heen proposed. 

The H NMR spectrum of thiirane 1-oxide is complex (AA BB ) at 60 MHz 24 lines are cfbserved consisting of two sets of 12 centered about a midpoint. The H NMR chemical shift in thiirane 1,1-dioxide is fairly sensitive to solvent variations partly because of the high dipole moment (4.4 D) of the sulfone. The benzene-induced shift, A5 (CeDe-CCLt), is large (-1.04 p.p.m.), as expected from the presence of a sulfone group. Oxygen-17 chemical shifts for thiirane 1-oxide and thiirane 1,1-oxide are -71 and +111 p.p.m. respectively, relative to H2O. 

Tungsten hexachloride and molybdenum pentafluoride desulfurize 2-methylthiirane to propene (72DOK(207)899) and a ruthenium(II) complex desulfurizes thiirane (73JA4758). 

Optically active thiiranes have been obtained by resolution of racemic mixtures by chiral tri-o-thymotide. The dextrorotatory thymotide prefers the (5,5)-enantiomer of 2,3-dimethylthiirane which forms a 2 1 host guest complex. A 30% enantiomeric excess of (5,5)-(—)-2,3-dimethylthiirane is obtained (80JA1157). 

Thiirane is more bactericidal than oxirane, and derivatives of 2-mei captomethylthiirane inhibit tuberculosis. The following pharmacological uses have been reported for compounds derived from thiirane derivatives gold complexes of the adducts of diethylphosphine and thiirane (antiarthritic), adducts of thiiranes and malononitrile (antibacterial, blood vessel dilators, muscle relaxants, sedatives), thermolysis products of thiirane 1-oxides and adducts of thiirane 1-oxides with sulfenyl chlorides (antibacterial), adducts of 2,3-diarylthiirene 1,1-dioxides with ynamines (antibacterial, parasiticidal), adducts of 2,3-diarylthiirene 1,1-dioxides with enamines (antifertility), adducts of p-aminophenylacetic esters with thiirane (immunosuppressants), adducts of amines and thiiranes (radioprotective drugs). 

Since a similarity between the rates of decomposition of thiirene dioxide complexes and those of thiirane dioxides was found, it was suggested103 that upon coordination the carbon-carbon bond order of thiirene dioxides decreases and the ligand becomes thiirane dioxide-like. The role of the metal is thus to saturate the carbon-carbon double bond so that the reactivity of the coordinated thiirene dioxide approaches that of the thermally less stable thiirane dioxide. 

Whereas acyclic sulfoxides form complexes with various metal salts, thiirane oxides react with copper(II) chloride or bromide163 in benzene at room temperature to give the thiolsulfonate 146a. In alcoholic solution below 0 °C the major products are sulfinates (149). Similar results are obtained in the reaction of thiirane oxides with ethanesulfinyl chloride163 as summarized in equation 60. 

Oxirane is an important Lewis base in the present context. The O atom carries two equivalent n-pairs of electrons, as it does in H20, but oxirane has the advantage over water in that it is possible to determine both angles 0 and 9 for its complexes with HC1 and ClF because the non-zero off-diagonal element Xab(Cl) of the Cl nuclear quadrupole coupling tensor is available. The corresponding Lewis base in which an S atom carries two equivalent n-pairs is thiirane. Each of the pair of complexes (CL S- -HC1 and (CL S- -ClF has Cs symmetry and here it is the off-diagonal element Xac(Cl) that is non-zero... 

Fig. 9 The experimentally determined geometries of thiirane- HC1 and thiirane- C1F drawn to scale. The n-pair model of thiirane is shown for comparison. The angle is slightly different in the two complexes for reasons discussed in [69]. The non-linearity 9 of the hydrogen bond is again greater than that of the halogen bond. See Fig. 1 for key to the colour coding of atoms...

Another synthesis of olefins has been described in which the desulphurization of thiirans by triphenylphosphine is featured.72 There have been many reports of the synthesis of compounds of the type (63). These form charge-transfer complexes with acceptors such as tetracyanoquinodimethane which have metallic properties. The... 

When thiocarbonyl derivatives are treated with an excess of electrophilic carbene complex, alkenes are usually obtained [1333-1336], The reaction is believed to proceed by the mechanism sketched in Figure 4.18, closely related to the thiocarbonyl olefination reaction developed by Eschenmoser [1337], Few examples have been reported in which stable thiiranes could be isolated [1338], The intermediate thiocarbonyl ylides can also undergo reactions similar to those of carhonyl ylides, e.g. 1,3-dipolar cycloadditions or 1,3-oxathiole formation [1338], Illustrative examples of these reactions are given in Table 4.22. 

When planning reactions of thiocarbonyl compounds with electrophilic carbene complexes it should be taken into aceount that thiocarbonyl compounds can undergo uncatalyzed 1,3-dipolar cycloaddition with acceptor-substituted diazomethanes to yield 1,3,4-thiadiazoles. These can either be stable or eliminate nitrogen to yield thiiranes or other products similar to those resulting from thiocarbonyl ylides [1338]. 

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