Phosphorus-nitrogen bonds synthesis

Amino groups can also serve to block a position on phosphorus (29, 49). To avoid nitrogen-phosphorus bond cleavage in the synthesis of 41, the lithium reagent was added to the phosphorus halide at —60° yield of 41 was 48% (49).. ... 

The degradation of a-aminocarboxylic acids has proven to be a useful method for the preparation of iminium salts. For example, treatment of N- methylpipecolic acid (97) with phosphorus oxychloride gave 94% of the iminium salt (98) (Scheme 7) (76JA7448). The synthetic utility of this approach is illustrated by the synthesis of tetrahydroberberine (Scheme 8) (78JOC2115). The advantage of this method for the preparation of iminium salts is that the position of the carbon-nitrogen double bond can be controlled. 

Before 1964 no stable compound with a localized or delocalized carbon-phosphorus double bond was known. Indeed, it was generally assumed that the atomic radius of phosphorus, being larger than that of carbon or nitrogen, would not provide sufficient 2pn—3pir overlap for such a ir system to be stable Our first communication, written jointly with Peter Hoffmann which described the synthesis of a stable phosphamethin-cyanine 1 with a delocalized P—C double bond was therefore received with skepticism However, after Allmann confirmed the structure by X-ray analysis the existence of a new type of phosphorus bond in a cationic delocalized tt system was unambigously established... 

The a-methoxylated derivatives are shown to be versatile synthons because of the reactivity of the methoxy group near the nitrogen atom, a-Methoxycarbamates, prepared by anodic oxidation, were used as key intermediates in the synthesis of a-amino acids,200 a new carbon-phosphorus bond-forming reaction,200 and in a new method of acylation of aliphatic amines at the -position.201 The application of this reaction to the synthesis of pyrrolidine, piperidine, and tropane alkaloids is also described.202... 

Amino, alkoxy, and aryloxy polyphosphazenes are typically prepared by nucleophilic displacement reactions of poly(dihalophosphazenes). Analogous reactions with organometallic reagents, however, result in chain degradation and cross linking rather than in linear, alkyl, or aryl substituted poly(phosphazenes). The thermolysis of appropriate silicon-nitrogen-phosphorus compounds can be used to prepare fully P—C bonded poly(organophosphazenes). The synthesis of two of these materials and their Si—N—P precursors is described here. 

Compounds that contain alternating phosphorus-nitrogen double bonds in then-skeleton are called phosphazenes. As historical background, Liebig first reported the synthesis procedure of chlorophosphazene (NPCl ), prepared by the reaction between phosphorus pentachloride with ammonia in 1834. Then Gladstone, Besson, Rosset, Couldridge, and Stokes furthered the fundamental chemistry of the phosphazene, i.e., substitution, hydrolysis, polymerization, and so forth, from 1850... 

No ji-coordination compounds with a coordinate bond from an aryl group to the metal of the type shown in compound 4.19 that are as stable as those in which the ligand atom is nitrogen, phosphorus, arsine, oxygen, or sulfur have yet been reported [19, 20] the synthesis of these 4.19 compounds is difficult, because p-elimination readily occurs in these alkyl compounds and the Group 6 metals chromium, molybdenum, and tungsten as shown in Fig. 4.5. 

Since amine-phosphorus(III) halide condensation reactions are well-established low-energy routes to phosphorus-nitrogen bonds, they provide a logical starting point for examination of skeletally stabilized molecule synthesis. For our initial studies, reactants that are phenyl substituted as opposed to alkyl substituted... 

The 1,2,4,3-triazaphospholes are colorless or pale yellow distillable liquids or crystalline solids. They are not oxidized by air and are reluctant to react with sulfur. Three isomeric heterocyclic systems of 277-1,2,4,3-triazaphospholes 15, 177-1,2,4,3-triazaphospholes 16, and 477-1,2,4,3-triazaphospholes 17 are known and they differ considerably in their behavior <1996CHEC-II(4)771>. The synthesis of 1,2,4,3-triazaphospholes and reactivity of different isomers of 1,2,4,3-triazaphospholes in the reactions at a ring nitrogen, in the addition to the P=N bond, oxidative addition to the ring phosphorus, cycloaddition reactions, and the formation of transition metal complexes are systematically covered in CHEC-II(1996) <1996CHEC-II(4)771>. The 1,3,4,2-thiadiazaphospholium ions 18 are only briefly mentioned in CHEC-II(1996) and no new results on their chemistry have been published in the last decade. 

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