Mechanisms and stereochemistry of displacement of methoxide ion by hydroxide ion from phosphorus in phospholanium and phosphorinanium salts

Marsi, Kenneth L.

doi:10.1021/jo00900a023

Cited by 27 publications

(12 citation statements)

References 7 publications

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“…To the best of our knowledge, such a structure has never been described. Only a quaternary phospholanium compound, which possesses two methoxy groups on the phosphorus atom, has been reported 21. Compounds 9 appear as oils, and no crystal could be obtained for X‐ray crystal structure analysis.…”

Section: Resultssupporting

confidence: 92%

OC004: The fetal neurology clinic. A multidisciplinary approach for the assessment of the fetus with suspected nervous system pathology

Malinger

Lev

Zahalka

et al. 2003

Ultrasound Obstet Gynecol

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Section: Resultssupporting

confidence: 92%

OC004: The fetal neurology clinic. A multidisciplinary approach for the assessment of the fetus with suspected nervous system pathology

Malinger

Lev

Zahalka

et al. 2003

Ultrasound Obstet Gynecol

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“…Likewise, the 3 Jp. ocHJ)coupling constants of 11.4 Hz for both isorners are in agreernent with the values previously reported by Marsi or phosphorus cyclic cornpounds [7]. Finally, the 31 P NMR signals for each isorner appear at +72.43pprn for 8a and +68.3 pprn for 8b.…”

Section: Introductionsupporting

confidence: 90%

“…When the benzyl group is used as the leaving group, the reaction with base is non-stereospecific yielding phosphine oxides as mixtures of different proportions [ 6]. However, when the more electronegative methoxy group is used as the leaving group, pure samples of cis and trans 4-methyl (la and lb) or 4-t-butyl (3a and 3b) afford the corresponding phosphine oxides 2 or 4 (Scheme 1) with complete inversion of configuration at phosphorus [7]. We have reported our results about the hydroxide-induced displacement ofthe methoxy groups on samples of pure cis and trans isomers of 3-methoxy-2,2,6-trimethyl-3-phenyl-1,3-oxaphosphorinanium tetrafluoroborate salts 5a and 5b (Scheme 2), systems designed to study the effect of a second heteroatom in the ring system on the stereochemistry of the reaction.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 3-oxo-3-Phenyl-2,2,5-trimethyl-1,3-oxaphosphorinanes and their tetrafluoroborate salts

et al. 2011

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The synthesis and characterization of cis- and trans- 3-oxo-3-phenyl-2,2,5-trimethyl-1,3-oxaphosphorinanes (7a and 7b) and their corresponding tetrafluoroborate salts (3a and 3b) , heterocyclic organophosphorus compounds not previously reported in the literature, was accomplished. They were fully characterized by 1H, 13C and 31PNMR. It was established the relative configuration of these compounds on the basis of an X-ray diffraction study of oxide 7a.

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“…In the conformationally rigid 3,5-dimethyl-2-R-2-oxo-l,3,2-dioxaphosphorinanes, exceptions to the rule have also been encountered. 15 Methiodides of the Dimethylphosphorinanes. Based on the 13C chemical shifts of C-4 and the 4-methyl group, which are found in the same region as the sulfide and oxide, it is possible to assign preferred conformation 15 to the methiodide ch,-p+^-^~y 1 CH, 15 of 1,4-dimethylphosphorinane.…”

Section: Ch3 8a 8bmentioning

confidence: 99%

Stereochemical consequences of C-methylation of 1-methylphosphorinane and its sulfide and oxide: a carbon-13 and phosphorus-31 nuclear magnetic resonance study

Quin¹,

Lee²

1978

J. Org. Chem.

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Placing a methyl at the 3 or 4 position of 1-methylphosphorinane results in conformational equilibria for both the cis and trans isomers that are strongly biased toward the form with equatorial C-methyl. This remains true when the phosphines are converted to sulfides, oxides, or methiodides. The steric demand of C-methyl is therefore considerably greater than that of P-methyl, a fact predicted fpr 1-methylphosphorinane by its AGO value of +0.35 kcal/ mol. I3C NMR spectroscopy was especially helpful in qualitatively analyzing the equilibria; the C-methyl and its carbon of attachment in a pair of isomers had little chemical shift variability, while P-methyl differed by 4-6 ppm, always with the axial methyl relatively upfield. Both the sulfides and the oxides have ring carbons 3 and 5 at higher field (2-3 ppm) when the sulfur or oxygen atoms are axial. This greater y effect for a single-atom substituent on phosphorus over a methyl group has been observed previously for the case of S, but not for 0. While 31P NMR shifts were sensitive to the stereochemistry about phosphorus, no consistency in the direction of the effect was present. For the phosphines, axial methyl caused the expected relatively upfield shift. This was observed also for the sulfides, hut the reverse effect prevailed for the oxides.Phosphorus-substituted phosphorinanes are of considerable interest because of the predominance of the conformer with axial substituent, over that with equatorial a t room temperature.2 For the 1-methyl derivative, the equilibrium constant (a s e) is estimated to be about 0.55, which gives AGO = +0.35 kcal/mol at 27 "C. This unusual result stems from a combination of a rather low enthalpy difference for the conformers (AHo = -0.68 kcal/mol) and a significant entropy effect (ASo = -3.4 eu). 1-Methylarsenane was later reported by another group to exhibit similar p h e n~m e n a .~We have continued our investigation of the 1-methylphosphorinane system by considering the consequences of placing methyl a t either the 3 or the 4 position, and then of adding sulfur, oxygen, or methyl to phosphorus to increase its covalency in these compounds. The synthesis and spectral properties of all of these compounds are reported in the present paper. Our major probe of the conformational changes occurring in these families has been I3C NMR spectroscopy; we have previously employed this technique for hydroxy4 and keto5 derivatives of phosphorinanes and have witnessed a number of useful effects. 31P NMR spectroscopy has also figured in our earlier studies and we have examined our new C-methyl compounds by this technique also.The spectral data we have accumulated are best interpreted on the basis of perturbation of the conformational equilibrium for the parent 1-methylphosphorinane (1). Thus, a more CH la l bspace-demanding group such as CH3 (AGO = -1.7 kcal/mol in cyclohexanes; for thianes,6 -1.80 f 0.10 for 4-CH3 and 1.40 f 0.07 for 3-CH3) placed on ring carbon 4 should control the equilibrium and the P-CHs group will be forced into greater oc...

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Mechanisms and stereochemistry of displacement of methoxide ion by hydroxide ion from phosphorus in phospholanium and phosphorinanium salts

Cited by 27 publications

References 7 publications

OC004: The fetal neurology clinic. A multidisciplinary approach for the assessment of the fetus with suspected nervous system pathology

OC004: The fetal neurology clinic. A multidisciplinary approach for the assessment of the fetus with suspected nervous system pathology

Synthesis of 3-oxo-3-Phenyl-2,2,5-trimethyl-1,3-oxaphosphorinanes and their tetrafluoroborate salts

Stereochemical consequences of C-methylation of 1-methylphosphorinane and its sulfide and oxide: a carbon-13 and phosphorus-31 nuclear magnetic resonance study

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