Phosphine sulfide, with amines

This procedure also incorporates the use of bis(3-dimethylamino-propyl)phenylphosphine as a combined amine-phosphine reagent. The merits of using this basic phosphine as opposed to a tertiary amine and a phosphine lies in the ease of workup. Excess phosphine and phosphine sulfide can be removed by extraction with aqueous dilute acid. 

A different approach to synthesize nonstabilized ylide complexes is the reaction of halomethyl-metallic precursors with the corresponding nucleophile EZ . This method is quite general and usually occurs in very mild reaction conditions. Platinum, rhodium, iron, and palladium complexes (21)-(25) (Scheme 8) have been prepared, using phosphines [79-83], amines [84], or sulfides [85] as nucleophiles. Some of the most representative examples are shown in Scheme 8. 

The complexes of borane (BH3) itself with amines, phosphines, dialkyl sulfides and carbon monoxide, the first representatives prepared only in die 1930s were thoroughly discussed in several books and reviews.2,9,25-36 Therefore, in this section, only a brief summary will be given outlining the most basic aspects of these compounds, whereas complexes of substituted boranes will be discussed in more detail. 

The equilibrium constants with nucleophiles such as tertiary amines are so large, that carbenium ions practically do not exist. Thus, tertiary amines and pyridine apparently react with carbenium ions irreversibly and therefore terminate carbocationic polymerizations. Somewhat weaker nucleophiles such as 2,6-dimethylpyridine (lutidine), sulfides, and tris(p-chlorophenyl)phosphine are good deactivators in vinyl ether polymerizations because they react reversibly with monomer, thus maintaining a low concentration of carbenium ions without causing elimination. However, the equilibrium constants in styrene and isobutene polymerizations with amines, sulfides, and phosphines are too large to generate a sufficient stationary concentration of carbenium ions to complete polymerization in a reasonable amount of time. 

The synthesis of TSOSs is analogous to non-functionalized ILs. Indeed, the same key steps can be applied depending on the nature of the cation and the anion. Quatemisation of tertiary amines, phosphines and sulfides with a functionalized alkyl halide affords the desired functionalized ammonium, phosphonium and sulfonium halides in usually... 

Organocopper reagents are the most reliable species for conjugate additions and a number of approaches towards chiral cuprates has been developed. The approaches are classified into two categories one is the chiral heterocuprate obtained by treatment with chiral alcohols, amines, sulfonamides, and thiols. The other involves organocopper compounds coordinated by chiral external ligands such as phosphines, sulfides, and oxazolines. 

Organoboranes possessing one B—C bond in the molecule can also be obtained by hydroborating alkenes and alkynes with heterosubstituted borane derivatives, especially dihalogenoboranes, which can be stabilized by complexation with amines, phosphines, ethers and sulfides. The last two are useful complexing agents for both the preparation and the reactions of dihalogenoboranes . The most convenient synthesis of dichloroborane etherate is the reaction of LiBH. with BCl, in Et,0 ... 

As pointed out above, nucleophiles such as sulfides, alcohols, amines, phosphines, halides, and halide ions readily attack sulfur radical cations forming S.-.S, S.-.O, S.-.N, S.-.P, and S.-.X species. Generation of Me2S , under pulse radiolysis conditions, by the reaction of Me2SO with H- in aqueous HC104 permitted the... 

The main difference from C, N, and O is that Si, P, and S can form more bonds than the first row elements. This is because they have more orbitals the five 3d orbitals added to the 3s and three 3p orbitals. Silicon forms tetrahedral silanes, rather like alkanes, but also forms stable five-valent anions. Phosphorus forms phosphines, rather like amines, but also tetrahedral phosphine oxides. Sulfur can have any coordination number horn zero to seven, forming sulfides, like ethers, and tetrahedral sulfones with six bonds to sulfur. And it is with sulfur that we start. 

Nitrenes for the most part being electron deficient are highly electrophilic intermediates and therefore react with nucleophiles of all types. Tertiary amines, phosphines, sulfides, and sulfoxides all react with nitrenes to give ylides, in a reaction that is the reverse of their formation. In practice, dimethyl sulfoxide (DMSO) is often the most convenient nucleophilic trap since it can be used as the reaction solvent, and gives relatively stable sulfoximides (Scheme 6.40). Azo compounds, which are formally nitrene dimers, are common by-products in many nitrene reactions. However, the dimerization of two highly reactive species in solution is extremely unlikely on statistical grounds, and therefore the mechanism of azo compound formation probably involves the reaction of a nitrene, as an electrophile, with its precursor. 

Conjugative Effects Ligands acting as n-donors generally cause blue-shifts . However, the n-donor does not have to be a real substituent at the subvalent silicon atom. Lewis bases which are matrix-isolated along with the silylene also induce blue-shifts by the formation of adducts. This was shown for phosphines, sulfides, amines, alcohols, ethers and carbon monoxide . As mentioned above, in the case of methylsUylene even the use of N2 as the matrix material instead of argon led to a blue-shift of 150 nm . ... 

Many of these reactions are reversible, and for the stronger nucleophiles they usually proceed the fastest. Typical examples are the addition of ammonia, amines, phosphines, and bisulfite. Alkaline conditions permit the addition of mercaptans, sulfides, ketones, nitroalkanes, and alcohols to acrylamide. Good examples of alcohol reactions are those involving polymeric alcohols such as poly(vinyl alcohol), cellulose, and starch. The alkaline conditions employed with these reactions result in partial hydrolysis of the amide, yielding mixed carbamojdethyl and carboxyethyl products. 

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