Solvent-induced stereospecific isomerization of an allylic alcohol to a homoallylic alcohol catalyzed by a chiral lithium amide

1998 ◽  
Vol 76 (6) ◽  
pp. 795-799 ◽  
Author(s):  
Per I Arvidsson ◽  
Maria Hansson ◽  
Agha Zul-Qarnain Khan ◽  
Per Ahlberg
Keyword(s):  
Proton Transfer ◽  
Diethyl Ether ◽  
Allylic Alcohol ◽  
Cyclohexene Oxide ◽  
Deuterium Labeling ◽  
Lithium Amide

Deprotonation of cyclohexene oxide, 1, by lithium (S)-2-(1-pyrrolidinylmethyl)pyrrolidide, 2-Li, on changing the solvent from tetrahydrofuran (THF) to, for example, 2,5-dimethyltetrahydrofuran (DMTHF) or diethyl ether (DEE) has been shown to yield, besides the lithium alkoxide of 2-cyclohexene-1-ol, 3-Li, the lithium alkoxide of the homoallylic alcohol 3-cyclohexene-1-ol, 4-Li. It was shown that compound 4-Li is formed from 3-Li. No such rearrangement has been observed in THF. We have now shown that the solvent-induced isomerization of the lithium alkoxide of (S)-3-methyl-2-cyclohexene-1-ol, (S)-5-Li, catalyzed by 2-Li to the lithium alkoxide of (S)-3-methyl-3-cyclohexene-1-ol, (S)-6-Li, is 100% stereospecific. Furthermore, deuterium-labeling experiments suggest that the rearrangement of the proton is close to 100% intramolecular.Key words: 1,3-proton transfer, chiral lithium amide, intramolecular, solvent-induced isomerization, stereospecific.

POTASSIUM DERIVATIVES OF FLUORENE AS INTERMEDIATES IN THE PREPARATION OF C9-SUBSTITUTED FLUORENES: II. COMPARATIVE REACTIVITIES OF THE ALKALI METALS, LITHIUM, SODIUM, AND POTASSIUM, WITH FLUORENE IN GLYCOL DIMETHYL ETHER, GLYCOL DIETHYL ETHER, TETRAHYDROFURAN, AND DIOXANE

1960 ◽  
Vol 38 (12) ◽  
pp. 2450-2456 ◽  
Author(s):  
G. W. H. Scherf ◽  
R. K. Brown
Keyword(s):  
Dimethyl Ether ◽  
Diethyl Ether ◽  
Organometallic Compound ◽  
Alkali Metals ◽  
Organometallic Compounds ◽  
Lithium Amide ◽  
Glycol Dimethyl Ether ◽  
Derivatives Of ◽  
Sodium And Potassium

In the solvents 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), tetrahydrofuran (THF), and dioxane, potassium reacts much more readily with fluorene than does sodium or lithium. Lithium is generally more reactive than is sodium. The order of effectiveness of the ethers is DME > DEE ≈ THF > dioxane. Although practically no reaction of these metals with fluorene occurs in toluene, the addition of small amounts of these ethers to toluene does accelerate such reaction. All three organometallic compounds are soluble in refluxing and cold (22°) DME, THF, and DEE except the 9-fluorenyllithium, which precipitates largely from cold DEE. The results are explained in terms of the relative electropositivities of the metals, their size, and the structure of the ethers. It is suggested that these ethers actually participate in the formation of the organometallic compound from the metal.Sodamide and lithium amide react as readily as or more readily than the metals with fluorene in DME to produce the organometallic compounds.Diphenylmethane and triphenylmethane react reasonably well with potassium in DME, but too slowly with lithium and sodium to be useful.

Proton transfer as a first step in ion-molecule reactions of diethyl ether and tetrahydrofuran

1976 ◽  
Vol 29 (8) ◽  
pp. 1837
Author(s):  
T McAllister
Keyword(s):  
Proton Transfer ◽  
Mass Spectrometer ◽  
Diethyl Ether ◽  
Cyclotron Resonance ◽  
Double Resonance ◽  
Ion Cyclotron Resonance ◽  
Ion Molecule Reactions ◽  
Ion Cyclotron

Mechanisms may be written for several of the ion-molecule reactions in tetrahydrofuran and diethyl ether for which the first step is protonation to give the ion (M+l)+. This hypothesis was tested inan ion cyclotron resonance mass spectrometer by double-resonance experiments on mixtures of each of the ethers with methane. It was shown that CH5+ is a precursor for the tetrahydrofuran reactions,but not, with one exception, for the diethyl ether reactions.

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