P-C compounds

The hydrido phosphazenes 27 themselves are quite valuable reagents and can be converted into halogenocyclophosphazenes upon treatment with chlorine, bromine, or iodine. The elusive cyclophosphazenes containing a P I bond have been synthesized in this manner (43). Another application of the hydrido phosphazenes is their deprotonation, leading to phosphazene anions, which provide a valuable route for other P-C compounds (161). The phosphazene anions can also be generated by the cleavage of the bicyclophosphazenes 25 with LiBEt3H (163). 

Keywords Phospha sugar Phosphorus heterocycle P - C compound Phospholene Phospholane... 

They occupy a connecting position between the historic phospha-methinecyanine cations synthesized by Dimroth as the first -P=C-compounds, and the dicyanophosphide anion (and they show indeed intermediate spectroscopic and structural data, Figure 2). In a metathetic reaction these ions afford salts which have the same composition as the above compounds. They are stable as crystals but surprisingly rearrange in solution even at room temperature e.g. on attempted recrystallization. The exchange could proceed via a diphosphetane betaine. 

Phosphaalkenes, P=C compounds with a trivalent phosphorus atom, can react with various C=C compounds, like maleimide (Scheme 9) <2002JOM(643)409>, cyclobutadienes (Equation 27) <1994T759>, and C C compounds, like ynamines (Scheme 10) <2003EJ0512>, to afford the corresponding phosphetanes and phosphetenes. 

Phosphorus ylides, P=C compounds with a pentavalent phosphorus atom, can give phosphetanes as well as phosphaalkenes. By the reaction of a stabilized phosphoms ylide with activated alkenes, the phosphetane ring is formed via a zwitterionic betaine <1997HAC157>. 

Insertion into a Si—P bond is also observed. Reaction of alkylbis(trimethylsilyl)phos-phanes 402 with alkylarylcarbodiimides affords the insertion products 403, which depending on the substituents can rearrange into the P=C compounds 404. ... 

Recently there has been interest in the synthesis of analogs of the naturally occurring mono- and diphosphate group. Corey and Volante ° have reported the alkylation of (dimethylphosphoryl)methyl-lithium with, for example, geranyl, famesyl and 3-methyl-2-butenyl bromides. Tlie products were assessed for their ability to inhibit the biosynthesis of squalene. McClard and coworkers described the alkylation of the phosphonylphosphinyl anion (14) to yield the P—C— P—C compounds, proven enzyme inhibitors (Scheme 13). The free acid derivatives were obtained by treatment of the alkylated products with bromotrimethylsilane. 

The use and significance of stereochemical reaction cycles in the reactions of chiral phosphines and phosphonium salts have been surveyed, and a major review of the chemistry of polycyclic C—P heterocycles, much of which is concerned with tertiary phosphines and phosphonium salts, has appeared. Procedures for the synthesis of a range of unidentate and polydentate phosphine ligands have been collected together in a single volume. Aspects of the chemistry of methylphosphines have been included in a review of recent developments in the chemistry of simple P-C compounds. ... 

The metallated phospha-alkenes (172) and (173) offer considerable potential for the synthesis of P=C compounds. Treatment of (172) with carbonyl compounds has given the 1-phospha-allenes (174), and... 

T. Hori, M. Horigucbi, A. Hayashi, Biochemistry of Natural P-C Compounds, Maruzen, Kyoto Branch Publishing Service, Kyoto, Japan, 1984. 

Of particular interest are A, o -P=C compounds which, like those containing -P=P, can be stabilised by the presence of strongly electron-withdrawing groups as in FjC-P=CF2 (3.18a), or by electron delocalisation as in phosphinine C5H5P (3.18b), or by the introduction of bulky groups such as Bu, trimethylsilyl, or 2,4,6 tri-terbutylphenyl to shield the reactive centres (3.18c). 

The less stable -P=C compounds tend to dimerise or form higher polymers (3.21), and the same considerations apply to -P=N- compounds (3.22), (3.23). 

There has so far been only limited success in attempts to produce P-C compounds directly from elemental phosphorus, although both white and red forms are subject to attack by a variety of nucleophilic reagents. These and other synthetic methods are discussed below in this chapter. Synthesis of P-C bonds has recently been comprehensively reviewed [21]. The synthesis of P=C and P=C bonds is dealt with in Sections 6.14 and 6.15 (see also Phospha-Wittig reaction (6.445)). Carbophosphenes can be obtained from carbophosphynes and vice versa (6.631,6.631a), although these are not general methods of preparation. 

There are other methods for preparing cyclophosphazenes containing P-C compounds. Condensation reactions involving the elimination MesSiX (X = Br, F) from N-(silyl)-P-(halogeno)phosphoranimines is a good method for the preparation of fully substituted alkyl- or arylcyclophosphazenes (see Eq. 3.19) [2, 14]. 

The use of dynamic mechanical analysis to calculate a r to compare useful temperature ranges for flexible P" C compounds is increasing. Unfortunately the of a flexible PVC product is often dependent... 

Compound Tablets of Aspirin and Opium, B.P.C.y Tablets of Aspirin and Phenacetin, B,P.C, Compound Tablets of Codeine, B,P, and Soluble Compound Tablets of Codeine, B.P,y see under Acetysalicylic Acid, p. 13. 

The method may be applied directly to the B.P.C. Compound Syrup of Ferrous Phosphate, none of the ingredients of which interferes take about 0 4 g of the syrup (calculated 2 35 to 2 40 per cent w/v phosphorus). 

Paste of Resorcinol and Sulphur, B.P.C. Compound Paste of Zinc, B.P. ... 

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