Substitution at phosphorus

Other reactions involve formation of C—S or C—P bonds by insertion of S02 and by substitution at phosphorus, respectively (examples 6 and 7, Table XI). 

Warren, S. and Williams, M.R., Electrophilic substitution at phosphorus dealkylation and decarboxylation of phosphinylformate esters, Chem. Com-mun., 180, 1969. 

The PHOX ligands can be varied by changing the substitution at phosphorus, the oxazoline ring, and the bridge and thus a high variety can be made available. They have been applied to many catalytic reactions leading to high ee s with the appropriate substitution pattern. 

The planarity of the tricoordinate phosphorus and thus the aromaticity of 4 can be influenced by substituents. It turns out from ab initio calculations that 7T-acceptor groups either at phosphorus or at the neighboring carbon have a planarizing effect. The barrier to planarity decreases to 1.56 kcal/mol (MP2/ 6-31G(d)) as a result of —BH2 substitution at phosphorus. The bond length alternation in the planar form of this substituted derivative increases in the... 

Platinum(II)15 and palladium(II)16 complexes of phosphorus trichloride undergo solvolysis in water and alcohols to form complexes with orthophosphorous acid or orthophosphite ligands (equation 6). Similar reactions occur between the palladium(II) phenyldichlorophosphine complex (8) and the diols ethyleneglycol and catechol, but new chelate rings are not formed (Scheme 2). Solvolysis also occurs with attack of diphenylphosphinic acid or a similar diphenylchlorophosphine complex (9) (equation 7). The palladium complexes (8) and (9) are unstable to excess methanol, water or base and undergo reduction. Similarly, the phosphorus trichloride gold(I) complex (10) is reduced by water, but forms stable products on reaction with alcohols (equation 8).15 During the above reactions, the phosphorus—metal bond remains intact and the overall process is one of substitution at phosphorus. 

On the other hand, evidence against an intermediate hypervalent tetracoordinated phosphorus anion in nucleophilic substitutions at phosphorus in tertiary phosphines was put forward by Kyba the fact that the substitution reaction 3 occurs with complete inversion of configuration at phosphorus was interpreted to mean that it proceeds without even one pseudorotation of 9, which makes the passage through such an intermediate unlikely ( ). 

Among the most important reactions in biochemistry are those that involve substitution at phosphorus in phosphates. These reactions are involved in energy transduction, replication, transcription and recombination of nucleic acids, metabolic regulation, and metabolic pathways including biosyntheses of nucleotides, amino acids, proteins, complex lipids and complex carbohydrates. They are among the most intensively studied proteins in biochemistry, both because of their fundamental importance and because they present special challenges as research subjects. 

There are two basic prerequisites for completing an enzymatic investigation involving substitution at phosphorus. A substrate for the subject enzyme must first be synthesized with a chirally substituted phosphorus at the reaction center. ATP is a concrete example with three potentially chiral phosphorus centers, each of which undergoes enzymatic substitution. The enzymatic bond cleavages resulting from substitution at P0, and Py are illustrated in Fig. 3. Substitution at Pa is catalyzed by nucleotidyltransferases and certain ATP-dependent synthetases, and substitution at Py is catalyzed by phosphotransferases, other ATP-dependent synthetases and... 

Stereochemistry of enzymatic substitution at phosphorus (c) Chiral metal-nucleotides... 

The stereochemical course of enzymatic substitution at phosphorus has been determined for over thirty enzymes. While most of these studies have been completed... 

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