Phosphorus nucleophiles reactions

Reaction with Phosphorus Nucleophiles. The ethyleneknine ring can be opened using phosphines (91) or alkaU metal phosphides (92) ... 

Kinetic studies have shown that the enolate and phosphorus nucleophiles all react at about the same rate. This suggests that the only step directly involving the nucleophile (step 2 of the propagation sequence) occurs at essentially the diffusion-controlled rate so that there is little selectivity among the individual nucleophiles. The synthetic potential of the reaction lies in the fact that other substituents which activate the halide to substitution are not required in this reaction, in contrast to aromatic nucleophilic substitution which proceeds by an addition-elimination mechanism (see Seetion 10.5). 

Phosphorus nucleophiles have received little attention compared with nitrogen nucleophiles in reactions with fluonnated systems Yields with phosphorus nucleophiles are sometimes low, but interesting materials are obtained [80, 81] (equations 42 and 43). 

When a Br nsted base functions catalytically by sharing an electron pair with a proton, it is acting as a general base catalyst, but when it shares the electron with an atom other than the proton it is (by definition) acting as a nucleophile. This other atom (electrophilic site) is usually carbon, but in organic chemistry it might also be, for example, phosphorus or silicon, whereas in inorganic chemistry it could be the central metal ion in a coordination complex. Here we consider nucleophilic reactions at unsaturated carbon, primarily at carbonyl carbon. Nucleophilic reactions of carboxylic acid derivatives have been well studied. These acyl transfer reactions can be represented by... 

The influence of substituents in Ar1 is characterized by negative p values (plot based on ordinary Hammett a constants)208. Reactions involving other types of phosphorus nucleophiles (e.g. PPh2Alk)208 and ArS02 ions as nucleophiles have also been studied209. The work has been extended to the study of a-azidosulfones but the reaction does not turn out to be analogous210. There is base-catalyzed abstraction of hydrogen ion from the a-carbon atom. 

A. Nucleophilic Reactions of the P=0 Group.—Tris(trifluoromethyl)-phosphine oxide (33) reacts with hexamethyldisiloxane to give a phos-phorane, whose n.m.r. spectrum at — 140 °C shows non-equivalent trifluoromethyl groups. Although this unusual reaction clearly involves nucleophilic attack of the phosphoryl oxygen on silicon at some stage of the reaction, a full study of the mechanism has not been published. Tertiary phosphine oxides can be converted cleanly into dichlorophos-phoranes (34) by treatment with two moles of phosphorus pentachloride. Alkylation of the sodium salt of tetraphenylmethylenediphosphine dioxide (35) with alkyl halides, in dimethyl sulphoxide, has been reported to... 

Sections I and J of Scheme 3.2 show reactions with sulfur and phosphorus nucleophiles. The reaction in Entry 25 is a useful method for introducing thiol groups. The solid thiourea is a convenient source of sulfur. A thiouronium ion is formed and this avoids competition from formation of a dialkyl sulfide. The intermediate is readily hydrolyzed by base. 

The reactions of white phosphorus with tetraalkylammonium cyanides in the presence of a crown ether in acetonitrile give rise to the dicyanophosphide ion, which is found to react with a variety of anionic phosphorus nucleophiles with displacement of cyanide ion to generate new P-P bonded compounds.7... 

The mechanism of the reaction is understood to involve direct attack of the phosphorus nucleophile on the electrophilic substrate generating the new C-P bond, as shown in Equation 3.7.144145... 

The objective of this work Is to establish a reaction mechanism between sodium perborate and several organophosphorus esters. By analogy we can then describe Its probable effects upon other phosphorus-based Insecticides. We conclude that the reactivity of sodium perborate toward five model compounds Is attributable to the nucleophilic reactions of hydroperoxyl anion, HO2 , produced by perborate dissociation In water. On this basis we predict that sodium perborate solutions will be effective chemical detoxicants for phosphorus ester Insecticides. 

The preference of a substituent to adopt an apical position in associative mechanisms for nucleophilic reactions on phosphorus. This property is discussed in detail by Benkovic and Shray and the interested reader will also wish to consult Westheimer. ... 

Substitution (type nucleophilic) reactions in which an electron-rich agent (or nucleophile) attacks and forms a transient or stable bond with an electron-poor center (often carbon or phosphorus in biological systems) which has undergone prior or simultaneous expulsion of the leaving group (or exiphile). 

Compared with the variety of existing carbon or nitrogen nucleophiles that were subjected to nucleophilic addition to there are few examples for phosphorus nucleophiles. Neutral trialkylphosphines turn out to be to less reactive for an effective addihon to Cjq even at elevated temperatures [114], Trialkylphosphine oxides show an increased reactivity. They form stable fullerene-substituted phosphine oxides [115] it is not yet clear if the reaction proceeds via a nucleophilic mechanism or a cycloaddition mechanism. Phosphine oxide addition takes place in refluxing toluene [115], At room temperature the charge-transfer complexes of with phosphine oxides such as tri-n-octylphosphine oxide or tri-n-butylphosphine oxide are verifiable and stable in soluhon [116],... 

Pyridine compounds in which phosphorus is directly attached to a ring carbon are relatively rare. Phosphorus nucleophiles are not able to replace ring hydrogen atoms in pyridines and pyridine 1-oxides. Some time ago it was found that pyridine yields a zwitterion (170) when it is heated under reflux in the presence of tetraphosphorus decasulfide (Scheme 105) (68MI20500). Recently, a product that contains a C—P bond was isolated after extended heating under the same conditions followed by treatment with hydrochloric acid (81 JCR(S)285). However, it is uncertain whether free pyridine undergoes reaction in this case. Attack by phosphorus nucleophiles on salts is well established. Af-Methylacridinium methosulfate affords a stable isolable 9,10-dihydro adduct (171) that readily forms a... 

Phosphoryl and nucleotidyl transfer enzymes are extremely important and widespread in biology. They have in common the catalysis of nucleophilic reactions of phosphorus esters, and the general requirement for divalent metal ions, particularly Mg11, for activity. This requirement has stimulated considerable interest in the catalytic roles of divalent metal ions in these reactions. 

This section emphasizes work done in the last few years. The reader is referred to other sources for reviews of older work236 or more general discussions of nucleophilic reactions at phosphorus.237"245 More general discussions of enzymic phosphoryl and nucleotidyl transfer are available,246 248 and the role of divalent metal ions has been reviewed.249"251... 

The stereochemistry of the Pd-catalyzed reaction of lithium diphenylthiophosphides with allyl acetates was determined using a 5-phenylcyclohex-2-enyl system. This phosphorus nucleophile was found to add exclusively via ligand addition (equation 197).224 386... 

Whereas p-keu> compounds are accessible as described through metallated phosphonic acid esters (the Co try-Kwh u low ski reaction), P-alkoxycarbonyl compounds 40 as starting materials for the Hor-ner-Wiulwsorth-Emmtms reaction are obtained via the Arbusox reaction, an Sn2 process involving phosphorus nucleophiles. 

The formation of acylnaphthalenes 225 occurs under mild conditions (catalysis by sodium rm-butoxide or with the use of the phase-transfer method and TEBA as catalyst), and it affords high yields (60-90%). In this connection, it is surprising to recall the opinion about the incapability of 2-benzopyrylium salts to take part in recyclization reactions with compounds possessing active methylene groups, with secondary amines, or with sulfur or phosphorus nucleophiles (71CB2984). 

A review (91 references) on electrophilic and nucleophilic reactions of trivalent phosphorus acid derivatives, reactions of two-coordinate phosphorus compounds, and miscellaneous reactions has appeared.228 Earlier in this review we looked at the heavy-atom isotope effects on reactions of Co(III)-bound /vnitrophenyl phosphate,186 the uranyl ion hydrolysis of /vnitrophcnyl phosphodiesters (218)-(220),190 and the Th(IV) hydrolysis of these.191... 

This type of map can be used to discuss the different types of nucleophilic displacement reaction. Using the simplified version shown in Fig. 2 we have already seen that SN1 reactions, for instance the solvolysis of triarylmethyl halides, go through the separated ions in the top right-hand corner (Swain et al., 1953 Ritchie, 1971). At the opposite extreme, nucleophilic substitution at centres where the number of ligands can be increased may proceed over the bottom left-hand corner of the diagram. Examples are acyl transfer reactions and substitution at tetrahedral phosphorus centres (Alder et al., 1971) as well as substitution at square planar transition metal compounds (Wilkins, 1974). The nucleophilic reactions studied by Ritchie (1976), for which the rate... 

Nucleophilic Reactions of (Silylamino)phosphines. The reactions of (silylamino)phosphines with simple aldehydes and ketones proceed via nucleophilic attack by phosphorus followed by a [1,4] silyl migration from nitrogen to oxygen to yield new N-silylphosphinimines ( 3). With a,B-unsaturated carbonyl compounds, 1,4-addi-... 

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