P-nucleophiles

For a monograph, see Harris, J.M. McManus, S.P. Nucleophilicity American Chemical Society Washington, 1987. For reviews, see Klumpp, G.W. Reactivity in Organic Chemistry Wiley NY, 1982, pp. 145, 181 Hudson, R.F. in Klopman Chemical Reactivity and Reaction Paths Wiley NY, 1974, p. 167. 

Addition ofN-, S- and P-Nucleophiles The reaction of nitrones with heteroatom centered nucleophiles has been little investigated and are mainly applied to the synthesis of new heterocyclic systems and stable nitroxyl radicals, containing a heteroatom at the a-carbon atom. 

Nitroglycals65 are excellent Michael-type acceptors,66 where O-, N-, S-, C- and P-nucleophiles can be used as donors.67 An application of this kind of reaction was reported by Schmidt et al. for a new synthesis of 2-deoxy-2-nitro-D-galactose nucleoside 86 and of /V-acetyl-D-galactosamine nucleoside 88, based on addition reactions to 3,4,6-tri-0-benzyl-2-nitro-D-galactal 85 (Scheme 28).68... 

Anti-Markovnikov Additions of 0-, N-, P-Nucleophiles to Triple Bonds with Ruthenium Catalysts... 

In an earlier report Bach and coworkers suggested that MesN and MesP had nearly the same gas-phase barriers with peroxyformic acid (AA 5 = 0.5 kcalmol", MP4//MP2/6-31G ) and that their relative reactivity in protic solvent is better attributed to a much greater ground-state solvation of the more basic tertiary amine than the polarizability of the phosphorus. In a more recent study, a 3.3 kcalmol" barrier difference was observed with HCO3H in favor of the P nucleophile at B3LYP/6-31- -G(d,p) (3.0 versus —0.3 kcalmol". Table 12). Thus, the less reactive f-BuO—OH is a more discriminating oxidant with a later TS and the difference in barrier heights for N versus P oxidation widens. These data also point out that rate differences should be compared for a common set of nucleophiles and that when you use oxidants of different reactivity you should... 

We have found that (AlkO)jP and (AlkO)2P(0)H in the presence of EtjN form stable a-complexes on the C-3 atom in 3 and 4. This is peculiar to the nature of P-nucleophilic reagents while charged nucleophiles as a rule form more thermodynamically stable C-1 complexes (j>). 

It is quite possible that P-nucleophiles are well suited to accomplish nucleophilic aromatic substitution either through a-complexes formation or through halogen attack. 

The acid-catalyzed amine disproportionation, R1NH2 + R2NH2 R1R2NH + NH3, always occurs in parallel with HDN. Mechanistically, it is another example of S>p nucleophilic substitution, namely, of the NH2 group... 

P-nucleophiles (— precursors for Wittig or Horner-Wadsworth-Emmons reaction)... 

Phosphonium salts of type 5 may react with P-nucleophiles to give the corresponding ylides, having pronouced nucleophilic properties. They react with aldehydes and ketones, forming terminal olefins 6. ... 

This chapter will describe various additions to alkynes as a way to generate functional intermediates. In the first section, general additions of O, N, and P nucleophiles will be presented. Ruthenium-catalyzed hydrosilylation of alkynes will be described as an addition reaction to alkynes followed by ruthenium-catalyzed addition of C nucleophiles. 

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