Succinimide thioethers

This reaction is analogous to 10-16. Primary and secondary alcohols can be converted to alkyl aryl sulfides (ROH RSAr) in high yields by treatment with BU3P and an V-(arylthio)succinimide in benzene. Thioethers RSR can be prepared from an alcohol ROH and a halide R Cl by treatment with tetra-methylthiourea Me2NC(=S)NMe2 followed by NaH. ... 

Enantiomer separation of various compounds such as barbituric acids, benzoin, MTH-proline, glutethimide, a-methyl-oc-phenyl-succinimide, y-phenyl-y-butyrolac-tone, methyl-mandelate, l-(2-naphthyl)ethanol, mecoprop methyl, diclofop methyl and fenoxaprop methyl by pressure supported CEC on a permethyl-P-cyclodextrin modified stationary phase was described by Wistuba and Schurig [42-44]. Three different separation beds were used (i) permethyl-P-cyclodextrin was covalently attached via a thioether to silica (Chira-Dex-silica) [42], permethyl-P-cyclodextrin was linked to a dimethylpolysiloxane and thermally immobilized (ii) on silica (Chirasil-Dex-silica) [43] or (iii) on a silica monolith (Chirasil-Dex-monolith) [44], respectively. 

Thio ethers. The reagent reacts with primary and secondary alcohols at 20° in the presence of tri- -butylphosphine (triphenylphosphine is not so effective) to form phenyl thioethers, tri-n-butylphosphine oxide, and succinimide. The reaction proceeds with inversion. It is limited to N-(aryIthio)succinimides, since N-(alkyIthio)succinimides are desulfurized by phosphines. 

Cyclic thioethers. An equimolar amount of N-dilorosuccinimide added in 3 portions at 20-25° with intermittent cooling during 15 min. to a soln. of thiepane in benzene, stirred 1 hr., rapidly filtered to remove succinimide, the soln. of the resulting 2-chlorothiepane added to ethereal methylmagnesium bromide at such a rate that the temp, is maintained at 10-15°, and stirred overnight 2-methyl-thiepane. Y 66%. F. e. s. D. L. Tuleen and R. H. Bennett, J. Heterocyclic Chem. 6,115 (1969). 

Thioethers are said to be conveniently prepared from alcohols under mild conditions by reaction with sulphenimides such as (70) in the presence of tri-butylphosphine [equation (17)]. Both the succinimide and phosphine oxide by-... 

This side reaction is relatively innocuous because the by-product is irreversibly bound to the polymer and only the yield is affected not the purity of the synthetic peptide. More disturbing is the succinimide ring formation at aspartyl residues exposed to HF. Alkylation of the indole ring in tryptophan, the phenolic side chain in tyrosine and the sulfur atom in methionine must be suppressed by the addition of scavengers. The often appUed anisole is less than unequivocal in this role it can be the source of methyl groups which convert the methionine thioether to a tertiary sulfonium derivative. The acid stable thioanisole seems to be a better scavenger. 

By analogy with the catalytic allylic alkylation performed with C-nucleo-philes described in Section 7.2.2.3, Plietker et al. used benzyl mercaptan as an S-nucleophile toward an isobutyl carbonate in the presence of an NHC-Fe complex 9. Allylic thioethers were obtained in 82% yield as a mixture of two regioisomers [eqn (7.7)]. The same group also investigated the sulfonylation of allylic carbonates with a-sulfonyl succinimides as S-nucleop-hiles. In this case, a base-free catalytic system generated in situ by thermal release of the SIMes carbene from its chloroform adduct in the presence of [Bu4N][Fe(CO)3(NO)] was adopted. Addition of DBU to the reaction mixtures allowed the one-pot synthesis of vinyl sulfones through a tandem iron-catalysed allylic sulfonylation/amine-catalysed isomerisation process. Remarkably, base-induced decomposition of the iron catalyst was not observed. 

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