Sulphur nucleophiles, addition

On the other hand, some evidence for the longer life-time of the intermediate formed with amines may be inferred from the formation of small amounts of (116a) from piperidine and /J-chloroacrylonitrile, in addition to the main substitution product. (116a) is also the sole substitution product with aniline (R1=Ph, R2 = H) but no such products were reported for reactions with oxygen or sulphur nucleophiles. For formation of (116a) the initially-formed carbanion should be long-lived enough as to attack another j8-chloroacrylonitrile molecule (Scotti and Frazza, 1964). 

Nucleophilic additions to the cyclopropene double bond are particularly well documented for strained and/or highly reactive derivatives " Thus bicyclo-[4.1.0]hept-l(7)-ene (139) can be trapped by oxygen, sulphur and carbon nucleophiles (equation 52) and the rapid reactions effect a syn-addition. Cyclopropenone dimethyl... 

Reactions with Sulphur Nucleophiles. The addition of Et2AlSPh to the vinyl-oxiran (159) in benzene at 25 °C for 1 hour gives the (Z)-vinyl alcohol (160) (91%) with about 2% of the ( )-isomer. A novel route to the phenoxathiins... 

Optically active sulfur containing compounds play a very important role in biochemistry as well as synthetic chemistry. The asymmetric conjugate addition of sulphur nucleophiles, or sulfa-Michael addition [379], provides a direct and versatile approach toward optically active sulfur compounds. This strategy is particularly valuable, since enantioselective nucleophilic additions to a C-S double bond, unlike those to carbonyls and imines, are not synthetically feasible. 

Reviews cover the topics alkynethiolates in synthesis " oxygen-exchange reactions of sulphoxides sulphonyldiazomethanes C—S bond cleavage acyl isothiocyanates radical reactions of sulphur compounds addition of sulphenyl halides to olefins " sulphenamidcs mercaptoethylation of amines sulphur as a chiral centre " stereochemistry of S and S " compounds " reductive cleavage of sulphides, synthetic uses of alkene- and alkyne-thiolates, and thio-Claisen rearrangements nucleophilic displacements at sulphur in disulphides aromatic... 

A major study addressing the synthesis, kinetics and mechanism of SnAt displacement of 6-halopurine nucleosides with nitrogen, oxygen and sulphur nucleophiles was reported by Liu and Robins [97] (Scheme 25). The 6-fluoro group of 69 was displaced with butylamine, aniline, methanol and KSCOMe. The well understood order of reactivity at the 6-position was switched when a weakly basic aniline was used, to be I > Br > Cl> > F. An autocatalytic induction period was identified and the addition of trifluoroacetic acid eliminated this lag time and returned the reactivity order to F>other halogens. 

In addition, arylations of several neutral nucleophiles to give cationic products are known (Scheme 6). Examples include carbon monoxide in the presence of alcohols (non-catalysed methoxycarbonylation) and amines tertiary amines and pyridine 22 oxygen nucleophiles such as pyridine AT-oxides sulphur nucleophiles such as diaryl-,22 alkyl(aryl)sulphides 2 phosphorus nucleophiles such as tri-... 

Machin, P. j., and P. G. Sammes Pyrazine Chemistry. Part VI. Addition of Sulphur Nucleophiles across Dehydrocyclodipeptides. J. C. S. Perkin Transactions I 1974, 698. 

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