Janusz Rachon

REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART VI. THE REACTION OF THE >P—O− ANIONS WITH BENZYL BROMIDES para-SUBSTITUTED IN THE PHENYL RING

Abstract The reaction of p-substituted benzyl bromides with the >P—O− ions in THF, alcohols and toluene as the solvents is described. According to the reduction potential of the p-substituted benzyl bromides and the solvent used the formation of the P—C bond, debromination and/or dimerization occur. The principal process is believed to be X-philic substitution, the dimers are formed through a secondary process via SET from the p-substituted benzyl anions into the p-substituted benzyl bromides.

REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART II. THE REACTION OF TRIVALENT PHOSPHORUS ACID SALTS WITH THE BENZYLIC HALIDES SYSTEM

Abstract The reaction of the benzylic halides systems with sodium dialkylphosphites as well as the sodium salt of dibenzylphosphine oxide in THF and alcohols as the solvents is described. According to the constitution of the starting materials, the formation of the P—C bond, dehalogenation or dimerization occurs. Probable mechanisms namely SET and X-philic substitution are discussed.

The direct preparation of the esters ofp-nitrobenzylphosphonic acid fromp-nitrobenzyl halides

The reaction of sodium diisopropyl phosphite with p-nitrobenzyl bromide was studied in detail by (1) isolation and identification of all products and (2) studying the effects of radical traps, such as dicyclohexylphosphine, di-tert-butylnitroxide, and the diisopropyl phosphite anion, on product distribution. The results of the experiments carried out are compatible with a proposed X-philic substitution/SET tandem mechanism. It was demonstrated that p-nitrobenzyl chloride is also a good single-electron acceptor from the p-nitrobenzyl anion. The anion radical derived from p-nitrobenzyl chloride decomposes into the p-nitrobenzyl radical, which couples with an appropriate anion if it is present in a high enough concentration in the reaction mixture, to produce the dimer or the p-nitrobenzylphosphonate.

REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART I. REDUCTIVE DEBROMINATION IN THE REACTIONS OF THE >P[sbnd]O− IONS WITH 2-BROMOESTERS

Abstract The reaction of α-bromocarboxylates with sodium dialkyl (diaryl) phosphites as well as sodium salt of dibenzylphosphine oxide in THF and alcohols as the solvents is described. Debromination of the starting materials occurs. Probable mechanisms namely SET and X-philic substitution are discussed.

REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART III.∗ THE >P—O−IONS IN REACTION WITH ACTIVATED ALKYL BROMIDES. ATTACK ON BROMINE vs ELECTRON TRANSFER

Abstract The mechanism of reductive debromination in the course of the reaction of sodium dialkyl (diaryl) phosphites as well as the sodium salt of dibenzylphosphine oxide with activated alkyl bromides in THF has been investigated. Probable mechanisms namely SET and X-philic substitution are discussed. The cyclopropyl system was chosen for the study of this reaction. The results of the carried out experiments (unrearranged products, no influence of light) suggest that the cyclopropyl radical intermediate (if it is formed) does not participate in the product-determining step of the reductive debromination under the action of the >P-O−ions.

The Reactions of Dialkyl Phosphites and Phosphine Oxides with Iodosylbenzene

The reaction of iodosylbenzene with >P(O)H type of acids (dialkyl phosphites, secondary phosphine oxides) was studied. The acids of >P(O)H type add to iodosylbenzene to yield intermediate 6 which in the aprotic solvents yields oxidation products, it means >P(O)OH acids and/or anhydride of >P(O)OP(O)< type. On the other hand if the reaction is performed in alcohol as a solvent in the presence of sodium alcoholate >P(O)OR ester is the major product.

May Dithiophosphoric Acid Participate in the SET Process

Recently we have developed a convenient method for the synthesis of S -thioacyl dithiophosphates 1 , excellent thioacylating reagents. When hydroxylamines with one bulky group or two substituents on the nitrogen atom are treated with S -thioacyl dithiophosphates 1 O -thioacyl hydroxylamines 3 are produced exclusively. What is more important, compounds 3 undergo interesting reaction with dithiophosphoric acid 4 yielding amine and acyl thiophosphoryl disulfide 5 . The disulfide 5 can be formed as a product of thiophilic attack of the dithiophosphate anion on the thiocarbonyl group in protonated O -thioacyl hydroxylamine 3 . On the other hand, it is well known that dithiophosphate anions easily undergo one electron oxidation. Hence the dithiophosphate anion can act as single electron donor and disulfide 5 can be formed as a product of the SET reaction. The influence of light and radical traps strongly suggests that the second possibility operates in the reaction in focus.

REACTIVITY OF THE ACIDS OF TRIVALENT PHOSPHORUS AND THEIR DERIVATIVES. PART IV. THE REACTION OF DIALKYLPHOSPHITE ANIONS WITH NITROBENZYL BROMIDES

Abstract The reaction of o-, m- and p-nitrobenzyl bromide with sodium dimethylphosphite as well as sodium diisopropylphosphite in THF and alcohols as the solvents is described. According to the constitution of the starting materials and the solvent used, the formation of the P–C bond, debromination or dimerization occurs. The principal process in o- and p-nitrobenzyl bromide and >P-O− anion systems is believed to be X-philic substitution, the dimer is formed through a secondary process via SET from the nitrobenzyl anion to nitrobenzyl bromide. Electron-transfer and proton-transfer processes in the nitrobenzyl bromide->P–O− systems are also discussed.

Unexpected Thioketene Derivative Formation During Thioacyl Dithiophosphate Synthesis

Abstract The scope and limitations of the thioacylation method using thioacyl dithiophosphates were investigated. Thioacyl dithiophosphates are formed in the reaction of acyl dithiophosphates with dithiophosphoric acid. However when the acyl moiety contains two α-substituents then a thioketene derivative is formed thus lowering the yield of expected thioacyl dithiophosphate.

New reaction of dithiophosphoric acids with O-thioacylhydroxylamines. Nucleophilic substitution or single electron transfer process?

Disubstituted or sterically hindered hydroxylamines react with bulky S-thioacyl dithiophosphates yielding O-thioacylhydroxylamines. The reaction of O-thioacylhydroxylamines with dithiophosphoric acids yields acyl thiophosphoryl disulfides and ammonium dithiophosphates. The influence of radical traps on the reaction yield strongly suggests that radicals are involved in the mechanism of the process. The low redox potential of dithiophosphates, the observed photochemical stability of O-thioacylhydroxylamines and the influence of light on acyl thiophosphoryl disulfides yield imply involvement of a single electron transfer process in the investigated reaction.