Phosphorus-containing Rings

The preparation of l-methylphosphorinan-4-ol (45) from the -4-one by a wide variety of reductive techniques resulted in the same, roughly equal. 

Swaelens and M. Anteunis, Bull. Soc. chim. beiges, 1969, 78, 321 Tetrahedron Letters, 1970, 561. 

The structure of l,l,4,4-tetraphenyl-l,4-diphosphoniacyclohexane didibromide (46) has been shown to be a chair.  

Two diastereoisomers of 2-ethoxy-4,5-dimethyl-2-oxo-l,2-oxaphosphori-nan have been prepared and separated by g.l.c. The 2,4-cw-4,5-cw-isomer (47) undergoes rapid ring inversion between two roughly equally populated chair conformations, whereas the other isomer (48), which is 0.9 kcal mol  

A report of the n.m.r. spectra of some five-member ring phosphites and related compounds is interpreted in terms of their probable conformations. Europium shift reagents have been used by two groups to simplify the n.m.r. spectra of some 2-alkyl-2-oxo-l,3,2-dioxaphosphorinans (50) and (51). The American group showed that increasing the amount of 

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Kyba and his coworkerswere also able to prepare a number of smaller, phosphorus-containing rings and several maeroeyeles containing both sulfur and phosphorus atoms. 

Two phosphorus-containing ring systems and one silicon-containing fused heterocycle belonging to the hetero-atomic arrangements of this chapter have been synthesized recently. The synthetic pathways are presented in Scheme 25. 

Ring Synthesis of Phosphorus-Containing Ring Systems 905... 

Also, 13C NMR assignments have been published for a recently synthesized phosphorus-containing ring system imidazo[l,2-r-][l,3,2]oxazaphosphinine 49 <1996TL977>. The chemical shifts as well as the /C P coupling constants are shown in Table 2. 

X-Ray.—The crystal and molecular structure of tri-o-tolylphosphine, its oxide, sulphide, and selenide (125) have been compared. The mean P—C bond lengths appear to be determined by the n-electron density along the P—C bond and intramolecular steric interactions, d-Orbital participation was considered to be of little importance.152 X-Ray diffraction established the structure of diphosphinofumarate (126)153 and showed that the phospholanium iodide (127) has an envelope ring with the methyl group at the point of the flap.154 The bicyclic phosphonium bromide (128) has a distorted half-chair phosphorus-containing ring, one of the P—C bonds in the... 

Cycloaddition reactions between phosphaalkenes or -alkynes and activated alkenes or alkynes are also an available synthetic route to the four-membered rings. These reactions afforded not only phosphorus-containing rings, such as phosphetanes, phosphetenes, and phosphetes, but also arsine-containing rings. 

Phosphorus-Containing Ring Systems. - The chiral a-diazophosphonic acid derivatives (289), (290) and (291) have been prepared from (-) ephedrine and (S,S)-N,N -dimethyl-l,2-diaminocyclohexane. Preliminary experiments suggest that the new chiral auxiliaries investigated exert little influence over the subsequent reactions of the derived rhodium (II) acetate-catalysed O-H and N-H insertion reactions. ... 

Phosphorus Containing Ring Systems. 1-Acyl allyl phosphonates (376) exposed to the action of m-CPBA in the presence of MgS04 are readily cyclized... 

Phosphorus-containing Ring Systems. - A range of new chiral oxazaphospholidine oxides 266 and 267 have been synthesised and used as catalysts in asymmetric reductions of ketones with diborane. Mannich-type cyclisation reactions of 5-amino-3-benzylthio-4-cyano(ethoxycarbonyl)pyrazoles with dichlorophenylphosphine and aromatic aldehydes in the presence of cation exchange resin have been used to prepare a number of 6-oxo-6-phospha-4,5,6-trihydroimidazolo[l,2-b]pyrazoles, e.g. 268. Some of these compounds have herbicidal activity and this report is typical of a number of similar ones in the Chinese literature. A number of metallocycles, e.g. 269, have been reported as products from reactions of transient zirconocene-benzyne intermediates with phosphaimines followed by sulfuration or selenation. ... 

For the most part, theoretical methods have been applied to the question of the aromaticity of the various phosphorus-containing ring systems, and this question is relevant only to systems with complete cyclic 7r-conjugation. Applications to other areas have been rare. 

Ring compounds are named by the oxa-thia-aza replacement nomenclature from the parent phosphorus-containing ring ... 

There are very many compounds based on simple phosphorus-containing ring systems, such as those represented by structures 3 and 4, which are essentially of the phosphonic or phosphinic acid types. To the extent that they are also heterocyclic compounds of phosphorus, their chemistry has also been considered separately... 

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