Some reactions of 2,4-dimethoxytetrahydropyrans

1969 ◽  
Vol 47 (17) ◽  
pp. 3099-3106 ◽  
Author(s):  
M. J. Baldwin ◽  
R. K. Brown
Keyword(s):  
Room Temperature ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Temperature Reaction ◽  
Trans Isomers ◽  
Kcal Mole ◽  
A Value ◽  
Cis And Trans Isomers ◽  
Acid Catalyzed ◽  
Cis And Trans

Acid-catalyzed elimination of methanol from 2,4-dimethoxytetrahydropyran (1) produces 2-methoxy-5,6-dihydro-2H-pyran (3) rather than the expected olefin 4-methoxy-3,4-dihydro-2H-pyran (2).The reaction of 1,3-dibromo-5,5-dimethylhydantoin with 3 in ether – methanol gives a 2:1 mixture of the isomers 3β-bromo-2α,4α-dimethoxytetrahydropyran (5a) and 3α-bromo-2α,4β-dimethoxytetrahydropyran (5b) respectively. A rationale is given to explain the preponderance of 5a over 5b and the highly selective attack of the bromine of the hydantoin and the methanol on C-3 and C-4 respectively of the double bond of 3. Reduction of 5ab with zinc in ethanol provides only compound 3.The room temperature reaction of 1 in a mixture of water and 1,2-dimethoxyethane containing Amberlite IR-120, produces 2-hydroxy-4-methoxytetrahydropyran (6) as an equilibrium mixture of cis and trans isomers in the ratio 1:1. This gave a value of 0.9 kcal/mole for the anomeric effect in 6. Pyrolysis of the derivative, 2-acetoxy-4-methoxytetrahydropyran failed to produce the olefin 2 and resulted only in extensive decomposition.

Cis- and trans-2,4-dimethoxytetrahydropyran. Models for the study of the anomeric effect

1968 ◽  
Vol 46 (9) ◽  
pp. 1543-1548 ◽  
Author(s):  
F. Sweet ◽  
R. K. Brown
Keyword(s):  
Good Yield ◽  
Methoxy Group ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Kcal Mole ◽  
Mild Acid Hydrolysis ◽  
Acid Catalyzed ◽  
Cis And Trans ◽  
Hydrolysis Of ◽  
Mild Acid

Acid-catalyzed methanolysis of 2-methoxy-5,6-dihydro-2H-pyran gave, in good yield, a 4.0:1.0 mixture of trans- and cis-2,4-dimethoxytetrahydropyran. Mild acid hydrolysis of 2-methoxy-5,6-dihydro-2H-pyran followed by acid-catalyzed reaction with methanol gave a cis-trans mixture of 4-hydroxy-2-methoxytetrahydropyran in very poor yield.From the equilibrium mixture of trans- and cis-2,4-dimethoxytetrahydropyran (4.0:1.0), the magnitude of the anomeric effect of the 2-methoxy group was calculated to be 1.4 kcal/mole.

scholarly journals Isolation and ldentification of 2,6- Dimethyl- and 2,2,6 -Trimethyl-4-piperidone, Artifacts Produced by the Reaction of Cigarette Smoke Condensate and Acetone

1978 ◽  
Vol 9 (4) ◽  
Author(s):  
W. N. Einolf ◽  
R. N. Ferguson ◽  
J. F. Whidby ◽  
J. F. DeBardeleben
Keyword(s):  
Reaction Time ◽  
Cigarette Smoke ◽  
Temperature Reaction ◽  
Cigarette Smoke Condensate ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans

AbstractCigarette smoke condensate (CSC) processed with acetone was found to contain 2,2,6-trimethyl-4-piperidone and the cis and trans isomers of 2,6-dimethyl-4-piperidone. The compounds were found to be artifacts formed by the reaction of the smoke components ammonia and acetaldehyde with the solvent acetone. Conditions which affected the yield of the artifacts from the processed CSC include pH, temperature, reaction time, and levels of ammonia and acetaldehyde present in CSC.

SYNTHESES IN THE TERPENE SERIES: VIII. SYNTHESIS OF THE CIS- AND TRANS-ISOMERS OF 7,7,10-TRIMETHYLDECAL-1-ONE. A CONVENIENT MODIFICATION OF THE BROWN HYDRATION REACTION

1959 ◽  
Vol 37 (11) ◽  
pp. 1870-1880 ◽  
Author(s):  
Franz Sondheimer ◽  
Saul Wolfe
Keyword(s):  
Trans Isomer ◽  
Raney Nickel ◽  
Equilibrium Mixture ◽  
Hydration Reaction ◽  
Trans Isomers ◽  
Perbenzoic Acid ◽  
Cis And Trans Isomers ◽  
Cis And Trans

7,7,10-Trimethyl-Δ1(9)-octal-2-one (VII) was converted to the cycloethylenedithioketal (VIII), which on Raney nickel reduction yielded 7,7,10-trimethyl-Δ1(9)-octalin (IX). Oxidation with perbenzoic acid led to the corresponding oxide (X), which could be rearranged in low yield to an equilibrium mixture of 7,7,10-trimethyldecal-1-one consisting essentially of the trans-isomer (XI).A convenient modification of the Brown hydration reaction is described, whereby the necessity of generating diborane or of using diglyme is avoided. 7,7,10-Trimethyl-Δ1(9)-octalin (IX) on Brown hydration using this modification stereospecifically furnished 7,7,10β-tri-methyl-cis-decal-1β-ol (XII), which was oxidized to 7,7,10-trimethyl-cis-decal-1-one (XIII). Isomerization resulted in the above-described equilibrium mixture containing at least 90% of the trans-isomer (XI). Similarly, the previously described 10-methyl-Δ1(9)-octalin (XVI) yielded a mixture of the cis- and trans-isomers of 10-methyldecal-1-one (XIX). Syntheses of 2-methylene-7,7,10-trimethyl-Δ1(9)-octalin (XIV) and of 7,7,10-trimethyl-cis-decal-2,3-dione 3-dithiotrimethylene ketal (XXII) are also described.

cis/trans Isomers of Dimeric Dialkylaluminum and Dialkylgallium Hydrazides

2008 ◽  
Vol 63 (10) ◽  
pp. 1149-1154 ◽  
Author(s):  
Werner Uhl ◽  
Andreas Vogelpohl
Keyword(s):  
Solid State ◽  
Equilibrium Mixture ◽  
Trans Configuration ◽  
Trans Isomers ◽  
Tert Butyl ◽  
Hydrazine Derivatives ◽  
Piperidine Derivative ◽  
Cis And Trans Isomers ◽  
Gallium Hydride ◽  
Cis And Trans

AbstractThe reaction of diethylaluminum hydride with the hydrazine derivatives 1-aminopyrrole and 1- aminopiperidine afforded the corresponding dialkylaluminum hydrazides (1 and 2) by the release of elemental hydrogen. Both products are dimeric in the solid state. While 1 adopts a cis arrangement of the pyrrole groups, a trans configuration was determined for the piperidine compound 2. Only 1 gives an equilibrium mixture of cis and trans isomers in solution. Similar compounds (3 and 4) were obtained by the treatment of the same hydrazines with di(tert-butyl)gallium hydride. Both products exhibit the trans configuration in the solid state, but interestingly only the piperidine derivative 4 shows a cis/trans equilibrium in solution.

Synthese von Silicium-Phosphor-Ringen - Struktur eines cis-2.2.4.4-Tetrakis(silylamino)-1.3-diphospha-2.4-disilacyclobutans / Synthesis of Silicon-Phosphorus-Rings - Structure of a cis-2,2,4,4-Tetrakis(silylamino)-1,3-diphospha-2,4-disilacyclobutane

1983 ◽  
Vol 38 (12) ◽  
pp. 1557-1562 ◽  
Author(s):  
Uwe Klingebiel ◽  
Norbert Vater ◽  
William Clegg ◽  
Martin Haase ◽  
George M. Sheldrick
Keyword(s):  
Crystal Structure ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Molar Ratio ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
By Products ◽  
Cis Isomer

Fluorosilylphosphanes of the type R2SiFPHR′ (R = CHMe2, CMe3, NMeSiMe3; R′ = H, C6H5; 1-4) are obtained in the reaction of difluorosilanes with lithiated phosphanes in a molar ratio 1:1. Diphosphasilanes (5, 6) and a difluorosilylphosphane (7) are isolated as by-products. 1-4 react with n-C4H9Li to give cyclic silylphosphanes, LiF, and C4H10 (8-11). Dilithiated 5 reacts with F2PN(CMe3)SiMe3 to form of a four-membered SiP3-ring 12. The 31P NMR spectra of 9 and 11 show signal coalescence for the cis-and trans-isomers at room temperature. The crystal structure of the cis-isomer of 11 has been determined. The substituted ring 13 is prepared in the reaction of lithiated 9 and Me2SiF2

Adduct Intermediates in the Side-chain Nitration of 1,4-Dimethylnaphthalene

1972 ◽  
Vol 50 (24) ◽  
pp. 3988-3992 ◽  
Author(s):  
Alfred Fischer ◽  
Alan Leslie Wilkinson
Keyword(s):  
Acetic Acid ◽  
Nitric Acid ◽  
Acetic Anhydride ◽  
Room Temperature ◽  
Methylene Chloride ◽  
Side Chain ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Naphthyl Acetate

cis and trans isomers of 1,4-dimethyl-4-nitro-1,4-dihydro-1-naphthyl acetate (1) have been isolated from a mixture of 1,4-dimethylnaphthalene and nitric acid in acetic anhydride by quenching at −40°. At room temperature only 1-methyl-4-nitromethylnaphthalene (4) is obtained. The conversion of 1,4-dimethylnaphthalene to 4 and of the cis (1a) and trans (1b) adducts to 4, by nitric acid in acetic anhydride, has been followed by n.m.r. 1,4-Dimethyl-4-nitro-1,4-dihydro-1-naphthyl nitrate (5) appears to be the immediate product from nitration of 1,4-dimethylnaphthalene in acetic anhydride, methylene chloride, or nitromethane. In acetic anhydride 5 is converted into 1. Decomposition of 1 in acetic acid gives 1,4-dimethyl-2-naphthyl acetate and some 4. The formation of 4 in this reaction is suppressed by urea.

Stereoelectronic control in acetal formation

1980 ◽  
Vol 58 (23) ◽  
pp. 2531-2531 ◽  
Author(s):  
Normand Beaulieu ◽  
Robert A. Dickinson ◽  
Pierre Deslongchamps
Keyword(s):  
Experimental Evidence ◽  
Room Temperature ◽  
Equilibrium Mixture ◽  
Anomeric Effect ◽  
Equilibrium Study ◽  
Stereoelectronic Effects ◽  
Stereoelectronic Control ◽  
Acidic Conditions ◽  
Cis And Trans

The cyclization under acidic conditions of bicyclic and monocyclic hydroxypropyl methoxytetrahydropyrans 1 and 4 is reported. At room température, compound 1 gives only cis tricyclic acetal 2. At reflux, compound 2 equilibrates to yield a mixture of cis and trans tricyclic acetals 2 (45%) and 3 (55%). Compound 4 gives directly the equilibrium mixture of cis and trans bicyclic acetals 5 (55%) and 6 (45%) at room température. The specific formation of 2 from 1 constitutes strong experimental evidence that acetal formation is controlled by stereoelectronic effects. The anomeric effect can be estimated [Formula: see text] from the equilibrium study of 2 and 3. This value confirms the result previously obtained by Descotes (9).

Acid-catalysed isomerization of ethyl 5-Hydroxy-7a-methyl-1-oxo-2,6,7,7a tetrahydro-1H-indene-4-carboxylate

1977 ◽  
Vol 30 (2) ◽  
pp. 443 ◽  
Author(s):  
DJ Collins ◽  
CW Tomkins
Keyword(s):  
Hydrogen Chloride ◽  
Room Temperature ◽  
Chloroform Solution ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans

Treatment of a chloroform solution of ethyl 5-hydroxy-7a-methyl-1-oxo- 2,6,7,7a-tetrahydro-1H-indene-4-carboxylate with dry hydrogen chloride at room temperature gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a,6,7,7a- tetrahydro-1H-indene-4-carboxylate, and the corresponding trans-hydrindan in the ratio 9 : 1. Hydrogenation of this mixture gave ethyl 5-hydroxy-7a-methyl-1-oxo-cis-3a,6,7,7a-tetrahydroindan-4-carboxylate, and ethyl t-7a-methyl-1,5-dioxo-r-3a,4,5,6,7,7a-hexa-hydroindan-c-4a- carboxylate, which were characterized by conversion into the cis and trans isomers of 7a-methylperhydroindan-1,5-dione, respectively.

Azido(imidazole)bis(acetylacetonato)cobalt(III) Complexes — Facile trans ⇋ cis Interconversion in Solution

1985 ◽  
Vol 40 (4) ◽  
pp. 470-476 ◽  
Author(s):  
J. K. Das ◽  
K. C. Dash
Keyword(s):  
Nmr Spectra ◽  
Equilibrium Mixture ◽  
Biologically Active ◽  
Trans Isomers ◽  
Active Ligand ◽  
Azide Ion ◽  
Cis And Trans Isomers ◽  
Neutral Base ◽  
Cis And Trans ◽  
C Nmr

A number of mixed-ligand complexes of cobalt(III) containing coordinated azide ion, acetyl- acetonatc anion and the neutral base imidazole and, having the general formula [Co(acac)2(N3)(Im)] (Im = imidazole or its derivatives) have been synthesised by the reaction of K[trans-Co(acac)2(N3)2] with the biologically active ligand imidazole or its derivatives. IR and electronic spectra alongwith 1H and 13C NMR spectra have been employed to characterise the complexes and determine their geometry. In contrast to the stable trans-[Co(acac)2(NO2)(Im)] complexes, these azido complexes arc shown to undergo facile trans ⇋ cis interconversion in CHCl3 solution. The NMR spectra (1H and 13C) can be interpreted by assuming the presence of an equilibrium mixture of the cis- and trans-isomers in solution.

On the structure and reactivity of a stabilized phosphorane: methyl (triphenylphosphoranylidene) acetate

1990 ◽  
Vol 68 (12) ◽  
pp. 2123-2128 ◽  
Author(s):  
Margaret H. Kayser ◽  
Donald L. Hooper
Keyword(s):  
Phthalic Anhydride ◽  
Carbonyl Compounds ◽  
Room Temperature ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans

In the absence of a source of acidic protons, methyl (triphenylphosphoranylidene)acetate 1 exists as a mixture of the cis and trans isomers even at room temperature. Acidic protons catalyze the interconversion of the two forms and facilitate the reaction of the ylide with active carbonyl compounds such as benzaldehyde or phthalic anhydride. Keywords: stabilized phosphoylide, structure, reactivity.

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