Organophosphorus routes

Oxidative reactions frequently represent a convenient preparative route to synthetic intermediates and end products This chapter includes oxidations of alkanes and cycloalkanes, alkenes and cycloalkenes, dienes, aromatic fluorocarbons, alcohols, phenols, ethers, aldehydes and ketones, carboxylic acids, nitrogen compounds, and organophosphorus, -sulfur, -selenium, -iodine, and -boron compounds... 

Diazaphospholes constitute the most widely investigated class of heterophospholes, the 67t-aromatic phosphorus heterocycles [1,2]. Diazaphospholes are unique in the manner that the five-membered ring incorporates one phosphorus atom. First diazaphosphole representative, i.e. 2//-[l,2,3 diazaphospholc was obtained as early as 1967 [3] and until 1980s the interest of organophosphorus chemists remained in the development of different synthetic routes and in investigating their varied reactivity due to the structural diversity within the class [4], On the basis of the relative positions of the three heteroatoms in the five-membered ring, six monocyclic diazaphosphole systems (A-F) are possible and all of them have been reported (Structure 1). 

The reaction between dialkyl phosphorocyanatidite and acyl cyanides in dichloro-methane at 0 °C parallels that between the same phosphite and 1,2-dicarbonyl compounds, and is probably initiated by attack of tervalent phosphorus on the carbonyl group the formation of O- and V-alkyl products, (30) and (29), is an indication of the probable nature (28) of an intermediate.25 The extension of the reaction (see Organophosphorus Chemistry , Vol. 7, pp. 108, 126) to include ethyl phosphorodicyanatidite and 1-keto-esters provides a route to the 5-phosphabicyclo-[3,2,0]heptanes (31) in high yields.26... 

A few organophosphorus insecticides are also phosphoramidates, hydrolysis of the P-N bond being considered a route of detoxification. This is exemplified by the metabolism of acephate (9.82, Fig. 9.15), whose mechanisms of activation and detoxification have recently been re-examined in mice to better understand the relative innocuity of the compound in mammals and its selective toxicity in insects [156],... 

The surface modification of an inorganic support with organophosphorus coupling agents (OPCA) is an extremely versatile route to hybrid materials. This route has been applied to a variety of supports, including metal oxides, metals, aluminosilicates, silica, metal hydroxides, and carbonates. 

Scheme 8 Two-step sol-gel route to hybrid organic-inorganic materials based on organophosphorus derivatives [206, 208]...

Despite the advantages, there is concern over the use of such containment methods because the fate of pesticides put into such sites is not well known ( 1 ). One such fate process is volatilization from the disposal site. Organophosphorus pesticide volatilization from water and soil is relatively unlnvestlgated, and if this route of loss occurs to an appreciable extent from disposal sites, a local respiratory hazard may exist. 

A. Zwierzak, ACS Symp. Ser. 171,169-172 (1981) N-Alkylation of Organophosphorus Amides. A New, Convenient Route to Primary and Secondary Amines". 

Deshpande, S.M. Mishra, S.L. Gajankush, R.B. Thakur, N.V. Koppikar, K.S. Recovery of high purity Y203 by solvent extraction route using organophosphorus extractants, Min. Process. Extr. Metall. Rev. 10 (1992) 267-273. 

Dehalogenation of P-fluorinated As-phosphaalkenes and cyclodimerization of the resulting intermediates is a useful route for the preparation of lAs,3As-diphosphetes 16 <1998ZFA1116>. Cycloaddition reactions of unsaturated organophosphorus compounds and their heavy atom analogues are the most frequently used preparative route to... 

Route 1, attack of the nucleophilic reagent leading to a hexacoordinate intermediate or transition state, has been given preference (11,12,247,306-308). A similar pathway has been also postulated in organophosphorus chemistry (309-311). This mechanism may account for many experimental observations. It does not, however, seem to be generally accepted as the most favorable route (see, for example, Refs. 243 and 290). Activation toward nucleophilic attack intuitively should be less effective in the extracoordination structure [Eq. (72), B] than in the silylonium ion (C), because of the higher positive charge and lower steric requirements of the Si center in the latter. 

The application of ideas primarily developed for pure carbon chemistry to the chemistry of organophosphorus compounds, especially sp2-hybridized phosphorus atoms, has again advanced the route for synthesis of the 1-phosphaallenes. 

The order of appearance and the eventual pattern and severity of the signs and symptoms depend upon the specific organophosphorus compound involved, the route of entry into the body, the size of a single dose, or the size, number, and spacing of multiple doses. 

It is not within the scope of this article to detail the preparative aspects of organophosphorus chemistry (see Phosphorus Organophosphorus Chemistry). We limit ourselves to indicating the two basic routes to phosphorus macrocycles. The first route utihzes the conventional synthetic methods of organometaUic chemistry and is illustrated by Ciampolini and coworkers here, but others could... 

In conclusion, we would thank our team of contributors for their efforts in writing for these volumes in recent years. As noted above, this volume may represent the end of an era which has extended over more than 35 years, the first volume having appeared in 1970 under the editorship of Professor Stuart Trippett. It would be a serious omission in writing this preface if we failed to note the passing of Professor Leopold Horner (1911-2005) who contributed so much to the development of organophosphorus chemistry, particularly to the development of routes to chiral phosphines and, of course, to the Horner modification of the Wittig reaction. 

Azamethiphos is well absorbed following oral administration to rats but much less effectively by the dermal route. Unlike many other organophosphorus insecticides, azamethiphos does not undergo bioactivation through the P450 monooxygenase pathway, as it is already in its active oxon form. 

Naled is moderately to highly toxic via the oral route, with oral LD50 values of 91 30mgkg in rats and mice. Dermal LD50 values were 1100 mg kg in rabbits and 800 mg kg in rats. Naled can cause dermatitis and sensitization, and can be corrosive to skin and eyes. Effects due to naled exposure are similar to those caused by other organophosphorus pesticides. 

VX is absorbed through the skin and respiratory system. Because it is nonvolatile, it may remain in place for weeks after dispersion and cause casualties. Thus, it is classified as a persistent agent. Although VX does not pose a major inhalation hazard in usual circumstances, by the inhalation route it is estimated to be 10 times as toxic as sarin. It is hydrolyzed by the enzyme organophosphorus (OP) hydrolase. 

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