| Isomerization of N,N-dimethylallylamine leads to formation of trans-N,N-dimethylpropenylamine when the isomerization is completed using conditions which allow equilibration to the thermodynamically most stable product. The formation of cis-N,N-dimethylpropenylamine is found when the allylic anion intermediate is reacted with water or when the base catalyzed isomerization is not permitted to undergo cis to trans isomerization subsequent to initial reaction. Direct observation of the intermediate anion by ('13)C and ('1)H NMR gives positive evidence for cis-(eta)('3)-lithio-N,N-dimethylallylamine. The isomerization of 1-methyl-1,2,3,6-tetrahydropyridine to 1-methyl-1,2,3,4-tetrahydropyridine was also examined but the intermediate allylic anion was not observed. The dimerization of this product to 1,2,3,4-tetrahydro-1-methyl-5-(1-methylpiperidin-2-yl)pyridine was found to occur under acidic conditions.; Formation of allylic anions from 3,6-dihydro-2H-pyran and 4-methyl-5,6-dihydro-2H-pyran was studied by ('13)C NMR and also addition of electrophiles at the gamma position of these anions yielded alcohols, specifically: 2,3-dihydro-4-(2-hydroxy-2-propyl)-4H-pyran, 2,3-dihydro-4-(hydroxymethyl)-4-methyl-4H-pyran, 2,3-dihydro-4-(2-hydroxy-2-propyl)-4-methyl-4H-pyran, and 2,3-dihydro-4-(diphenylhydroxymethyl)-4-methyl-4H-pyran. These alcohols underwent acid catalyzed ring closure to form new acetal compounds, namely, 6,6-dimethyl-2,7-dioxabicyclo{lcub}3.2.1{rcub}octane, 5-methyl-2,7-dioxabicyclo{lcub}3.2.1{rcub}octane, 5,6,6-trimethyl-2,7-dioxabicyclo{lcub}3.2.1{rcub}octane, and 6,6-diphenyl-5-methyl-2,7-dioxabicyclo{lcub}3.2.1{rcub}octane.; Tetrahydrofuran, 2,5-dihydrofuran, and 2,3-dihydrooxepin were reacted with alkyllithium reagents to provide the lithium enolate of acetaldehyde, 1-lithio-Z,E-1-oxapentadienylate, and 1-lithio-1-oxaheptadienylate (configuration undetermined), respectively. These vinylogs of enolates were observed by ('13)C NMR and the chemical shifts were correlated with pi charge densities calculated by CNDO/2.; Vinyl anions were prepared and examined by ('13)C NMR including 6-lithio-2,3-dihydro-4H-pyran, 5-lithio-2,3-dihydrofuran, 1-lithio-1-ethoxyethene, and 7-lithio-2,3,4,5-tetrahydrooxepin. Preliminary metalation study of 4,5-dihydrooxepin gave inconclusive results. Reaction of these various anions with electrophiles yielded facile syntheses of several species which were reported while this work was in progress including 2,3-dihydro-6-(1-hydroxy-1-ethyl)-4H-pyran, 2,3-dihydro-6-(hydroxyphenylmethyl)-4H-pyran, 2,3-dihydro-6-(2-hydroxy-2-propyl)-4H-pyran, and 2,3-dihydro-6-(diphenylhydroxymethyl)-4H-pyran. One additional alcohol was prepared in this series being 2,3-dihydro-6-(2-hydroxyfuran-2-yl)-4H-pyran. Several of these alcohols were treated with various reagents and provided syntheses of 2-methyl-1,4-dioxaspiro{lcub}2.5{rcub}octane, 2-phenyl-1,4-dioxaspiro{lcub}2.5{rcub}octane, 8,16-diphenyl-1,7,10,15-tetraoxadispiro{lcub}5.2.5.2{rcub}hexadecane, (2,3-dihydro-4H-pyran-6-yl)phenylketone, 2-methyl-3-oxepanone, 2,2-dimethyl-3-oxepanone, 2-phenyl-3-oxepanone, 2,2-diphenyl-3-oxepanone, and 6-(diphenylmethylene)-2,3-dihydro-6H-pyran. The preparation of 2,3-dihydro-5-(hydroxyphenylmethyl)furan and dimerization to 6,13-diphenyl-1,5,8,12-tetraoxadispiro{lcub}4.2.4.2{rcub}tetradecane and formation of 7-(2-hydroxy-2-propyl)-2,3,4,5-tetrahydrooxepin are presented as well. Starting materials for some of the anions were prepared by modifications of existing syntheses for 3,6-dihydro-2H-pyran, 2,3,4,5-tetrahydrooxepin, cis- and trans-divinyloxirane, and 4,5-dihydrooxepin. |
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