Reactivity of hexachlorocyclotriphosphazene towards alkyl-lithium reagents

Winter, Heinrich; Vandegrampel, Jc

doi:10.1039/dt9860001269

Cited by 11 publications

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“…Allcock has shown that the reactions of Grignard reagents with hexachlorocyclotriphosphazene, N 3 P 3 Cl 6 , proceed by a halogen abstraction pathway, leading to metalated phosphazene intermediates . A similar pathway is followed in the reactions of organolithium reagents. , The corresponding reactions with hexafluorocyclotriphosphazene, N 3 P 3 F 6 , are more typical of the nucleophilic substitutions referred to above. ,, A geminal pathway is preferred for certain alkyl, ,, alkenyl, , phenylethynyl, , and trimethylsilylethynyl lithium reagents, while nongeminal products are obtained for a variety of aryllithium reagents , and t -butyl lithium . With the exception of the region and stereospecific t -butyl lithium case, the observed pathways are all regioselective with nongeminal products accompanying geminal products. , The resulting organofunctional phosphazenes have proved to be useful synthetic intermediates.…”

Section: Introductionmentioning

confidence: 80%

“…These observations provide added insight into the factors which control the reaction pathways followed by carbanionic nucleophiles in reactions with cyclophosphazenes. We have previously shown that the halogen abstraction mechanism which controls the reactions of Grignard and organolithium reagents with chlorophosphazenes ,, plays, at best, a minor role in the reactions of 1 , so one can assume that nucleophilic substitution is the dominant mechanism. It is a general observation in the reactions of chlorophosphazenes that geminally substituted products arise from dissociative processes .…”

Section: Resultsmentioning

confidence: 99%

“…6 A similar pathway is followed in the reactions of organolithium reagents. 6,7 The corresponding reactions with hexafluorocyclotriphosphazene, N 3 P 3 F 6 , are more typical of the nucleophilic substitutions referred to above. 2,6,8 A geminal pathway is preferred for certain alkyl, 2,9,10 alkenyl, 2,11 phenylethynyl, 12,13 and trimethylsilylethynyl 13 lithium reagents, while nongeminal products are obtained for a variety of aryllithium reagents 2,14 and t-butyl lithium.…”

Section: ■ Introductionmentioning

confidence: 95%

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Organophosphazenes. 26. Factors Controlling the Pathways Observed in the Reactions of Ethynyl Lithium Reagents with Hexafluorocyclotriphosphazene

Bahadur

Allen

2012

Inorg. Chem.

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In contrast to previously studied reactions of ethynyl lithium reagents, the reactions of propynyl and hexynyl lithium with N(3)P(3)F(6) lead to predominantly nongeminal isomers. A modest cis stereo selectivity was observed. The sequential addition of a lithio acetylene reagent which follows a predominately geminal pathway (lithiophenylacetylene) and an aryl lithium reagent (p-propenylphenyl lithium) which follows a predominantly nongeminal pathway were examined. The relative order of addition of the two reagents was interchanged, resulting in a change of reaction pathway demonstrating ring substituent control of the regio and stereo chemical pathways. Hydrogenation of the ethynyl unit in the phosphazene derivatives provides a facile pathway to the difficult to prepare alkylphosphazenes. The chemical shift of the organosubstituted phosphorus center undergoes a remarkably large change (46-47 ppm) on going from the ethynyl to the alkyl derivatives, which reduces the complex (31)P and (19)F NMR spectra of the ethynyl derivatives to easily interpretable first-order spectra, thus allowing for structure assignment. The (13)C NMR data shows that nongeminal regio selectivity increases with the amount of s character on the ethynyl carbon atom attached to the phosphorus center. These observations allow for an understanding of the factors controlling regio and stereo chemical control in the reactions of carbanionic nucleophiles with N(3)P(3)F(6).

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Section: Introductionmentioning

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 95%

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Organophosphazenes. 26. Factors Controlling the Pathways Observed in the Reactions of Ethynyl Lithium Reagents with Hexafluorocyclotriphosphazene

Bahadur

Allen

2012

Inorg. Chem.

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“…Reaction of compound (6) with LiBu', in molar ratio 1 : 1, and 2-propanol gave a mixture of the starting material (6) (20%) and (9a), (9b) (30%, molar ratio 14: 1). The 31P n.m.r.…”

Section: Resultsmentioning

confidence: 99%

Reactivity of cyclothiaphosphazenes towards alkyl-lithium reagents

Winter¹,

Vandegrampel²

1986

J. Chem. Soc., Dalton Trans.

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Reactions of (NPCI,),( NSOPh),-, ( n = 1 or 2) with 1 and 2 equivalents of LiMe or L i b t and an excess of 2-propanol in tetrahydrofuran lead to complex reaction mixtures, containing the hydridoisopropoxycyclothiaphosphazenes NPH(OPri)(NPCI,),(NSOPh),-, ( n = 0 or 1 ) and several alkyl-substituted ring systems (based on , ' P and 'H n.m.r. spectrometry). The structural characterization of the reaction products is described together with the appropriate reaction pathways, based on an initial metal-halogen exchange process. Reactions of the cyciothiaphosphazenes with alkyl-lithium reagents show a tendency to afford lower yields of cyclic derivatives than those previously reported for (NPCI,),. This different behaviour is ascribed to competition between the metal-halogen exchange process and nucleophilic substitution, which is supposed to induce ring cleavage.

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“…The crystal and molecular structure of the bicyclic compound [NPMe( NSOPh),],.C,H, has been determined. Two different pathways can be discerned for reactions of the ring systems (NPCl,),(NSOPh),-,[n = 1, (l), or 21 and (NPCI,), (2) with Grignard or organolithium reagents and an excess of propan-2-01 in tetrahydrofuran: (i) metal-halogen exchange and (ii) nucleophilic substit~tion. '~ The former process is assumed to proceed via a metallophosphazene intermediate in which a halogenomagnesium residue (MgX) or lithium is co-ordinated to a nitrogen together with a neighbouring trivalent phosphorus atom (see Scheme 1).…”

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confidence: 99%