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cesium ions which has been previously postulated and
References
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10. Representative experimental procedure: To a suspension
,
containing activated powdered 4 A molecular sieves (500
mg) in anhydrous N,N-dimethylformamide (8.3 mL)
cesium hydroxide monohydrate (180 mg, 1.07 mmol) was
added and the mixture was stirred under a dry nitrogen
atmosphere. After 1 (0.19 mL, 1.07 mmol) was added, the
reaction mixture was stirred for 1 h resulting in a dark
red–orange solution. Benzyl bromide (12) (0.15 mL, 1.29
mmol) was added in one portion, at which point, the
mixture turned immediately to milky white. The reaction
was allowed to proceed at room temperature for 26 h, at
which point 1 was consumed (TLC). Degassed basic
water (30 mL) was added and the mixture was subse-
quently extracted with CH2Cl2 (3×30 mL). The combined
organic layers were then washed with degassed basic
water (3×30 mL), dried using anhydrous sodium sulfate,
decanted, and the solvent was removed in vacuo. Purifi-
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air-sensitive white powder (275 mg, 93%).
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8. Molecular sieves accelerated the alkylation by removal of
water from the reaction media. When molecular sieves
were not activated, reactions were sluggish resulting in
diminished product yield with recovery of the starting
phosphine predominately.
9. It is plausible the reaction proceeds via the diphenylphos-
phide anion, which is prepared in situ by reaction of
Ph2PH and CsOH. The anion, presumably is weakly
coordinated to the cesium cation, hence, a ‘naked anion’
demonstrating enhanced nucleophilicity, as defined by the
‘cesium effect’. Preliminary observations are consistent
with previously reported examples using other alkali
metal counterparts. Currently, the mechanism is under
investigation and these results will be reported in due
course. For formation of ‘naked anions’ by solvation of
13. 31P NMR spectra were obtained for both crude and
purified products substantiating the claim for complete
specificity and purity for each tertiary phosphine. Phos-
phonium salt and side products stemming from elimina-
tion and oxidation of the phosphine were not detected in
an example. In addition, 1H, 13C NMR, GC/MS and
elemental analysis were carried out on all synthetic sam-
ples. All isolated final products gave analytical and spec-
troscopic data in agreement with the proposed structures.
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