Nucleophilic addition reactions sulphur nucleophiles

Mustard reacts with a wide variety of nucleophiles. Exemplified within this class of reactivity are reactions with hydroxide ion (hydrolysis) and reactions with sulphur and nitrogen nucleophiles. In addition, divalent sulphur is electron rich, and consequently mustard is also attacked by electrophiles. Oxidation, chlorination and complexation typify this class of reactions. Recent studies have also explored the possibility of using biomimetic systems (catalase) to achieve facile oxidation of mustard by peroxide moieties. 

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... 

Nucleophilic Attack on Oxygen or Sulphur.— The reactions of two bicyclic phosphoramidites, (35) and (36), with diethyl peroxide or diphenyl disulphide have been studied. Based on ring-strain arguments, the higher rate of (35) with diethyl peroxide, and of (36) with diphenyl disulphide, is considered support for a biphilic insertion mechanism for the addition of diethyl peroxide, and an... 

A number of interesting reactions of the dimer (66) with nucleophiles have been described. Addition of sodium methoxide in methanol yields dimethoxy-ether (71), by replacement of the olefinic fluorine atom and of an allylic fluorine, which in turn yields keten (72) by reaction with sulphur trioxide at 30—40 Diverse... 

Two-co-ordinate sulphur. Opinions seem divided as to whether nucleophilic attack at two-co-ordinate sulphur,which is an associative process, has a synchronous or an addition-elimination mechanism. For reaction of diaryl sulphides with aromatic hydrocarbons, formation of a sulphonium cation and then of a four-co-ordinate sulphur intermediate has been proposed. The role of the "id orbitals on sulphur in nucleophilic substitutions has been discussed. ... 

The grevillins are easily converted into crystalline yellow peracetyl derivatives with acetic anhydride and a trace of concentrated sulphuric acid (Table 2) 204, 461, 603). On catalytic hydrogenation the grevillins yield colourless dihydro derivatives in which reduction of the exocyclic double bond has taken place 603). Conjugate addition of nucleophiles to the exocyclic enone system leading to colourless by-products has also been observed during acetylation of these pigments 101) and in their reaction with diazomethane in methanol 276, 461). 

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