Reactions, with thioethers

Ring-opened adducts of carboplatin can form not only from reactions with nucleotides, but also by the attack of sulfur amino acids [44]. Reactions with thioether ligands are much more rapid compared with thiols. Surprisingly very stable ring-opened species such as [Pt(CBDCA-0)(NH3)2(L-HMet-S)] are formed, which has a half-life for Met-S,N closure of 28 h at 310 K. Such an intermediate could also play a role in the biological activity of this drug. 

This reaction involves the proton abstraction by a f-butoxy radical, followed by the coupling between a Sn2 reaction with thioether, as shown here. 

The relative kinetic cis effects of halide ligands on substitution at palladium(ii) have been established by monitoring the reactions of trans-[Pd(4-Cl-py)2Xa] and of rra j-[Pd(py)2Xa], where X = Cl, Br, or I, with amines or with thioethers in 1,2-dimethoxyethane solution at 25 °C. The usual two-term rate law [equation (4)] applies to these reactions, but as the ky terms were all small, the c r-effect trends have been reported only for the k, terms. The cis effects on substrate discrimination are in the order I>Br> Cl for reaction with amines, and Cl>Br>I for reaction with thioethers. This pattern is the same as that established for platinum(n) complexes, ... 

The reaction of thioethers with ethyleneimine in the presence of acid yields sulfonium compounds. The reaction is reversible under alkaline conditions (125). Compounds in which double-bonded sulfur can exist in tautomerism with a form having a free SH group, such as thiourea (126,127), thiocarboxyhc acids (128), and thiophosphates (129), react to give aminoaLkylated products. The P-aminoethyl thiocarboxylate rearranges to give the amide. 

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

Experiments with cyclic thioethers (80JCS(P1)1693), thiourea, thiocyanate and ethyl xan-thate always led to destruction of oxaziridines (73AJC2159). Products of complicated consecutive reactions could be isolated but only with some difficulty, e.g. (92) from a reaction with carbon disulfide (74JOC957), and (93), obtained by trapping with butadiene a product of a reaction between an oxaziridine and a thiirane (80JOC1691). 

This reaction is analogous to 10-7. It may be acid (including Lewis acids),base, or alumina catalyzed, occur with electrolysis, and may occur by either an SnI or Sn2 mechanism. Many of the P-hydroxy ethers produced in this way are valuable solvents, for example, diethylene glycol, Cellosolve, and so on. Reaction with thiols leads to hydroxy thioethers. Aziridines can similarly be converted to P-amino ethers. 

This reaction is catalyzed by the presence of divalent sulfur — e.g. sulfur ions, substances with S-S links, thioethers, thiazoles. If such substances are present in a chromatogram zone then the iodine applied with the reagent is consumed by reaction with sodium azide according to the above reaction. It is no longer available for the for-... 

Catalytic hydrogenation with platinum liberates the hydrocarbon from methylcobalamin (57) and from alkyl-Co-DMG complexes (161), but not from pentacyanides with primary alkyl, vinyl, or benzyl ligands, though the cr-allyl complex yields propylene (109). Sodium sand gives mixtures of hydrocarbons with the alkyl-Co-salen complexes (64). Dithioerythritol will liberate methane from a variety of methyl complexes [cobalamin, DMG, DMG-BF2, G, DPG, CHD, salen, and (DO)(DOH)pn] (156), as will 1,4-butanedithiol from the DMG complex (157), and certain unspecified thiols will reduce DMG complexes with substituted alkyl ligands (e.g., C0-CH2COOH ->CH3C00H) (163, 164). Reaction with thiols can also lead to the formation of thioethers (see Section C,3). 

Test reaction with furanoside thioether-phosphite or -phosphinite ligands. 

Scheme 1.33 Test reaction with (+ )-camphor-derived pyridine thioether ligand.

Scheme 1.36 Test reaction with pyridine thioether and dithioether ligands.

Scheme 1.40 Test reaction with pyrrolidine thioether ligands.

Scheme 1.43 Test reaction with oxazolidine-thioether and thiazolidine-methanol ligands.

In 2007, Fernandez et al. demonstrated that transition-metal complexes with heterobidentate S/C ligands based on imidazopyridin-3-ylidene and thioether functionalities could be readily prepared from the corresponding azolium salts by reaction with Ag20 and transmetalation of the resulting silver carbenes with appropriate metal sources. The cationic Pd(allyl)(carbene-S) complexes have proven to be active catalysts in the test reaction, reaching enantioselectivities of... 

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