Albert Padwa - Academia.edu (original) (raw)
Papers by Albert Padwa
Chemical and Pharmaceutical Bulletin, 1995
Angewandte Chemie International Edition, 2003
Bulletin of the Chemical Society of Japan, 1976
A Critical Review of the 1993 Literature Preceded by Two Chapters on Current Heterocyclic Topics, 1994
Journal of the American Chemical Society, 1965
Journal of the American Chemical Society, 1963
ABSTRACT
Journal of the American Chemical Society, 1963
ABSTRACT
Journal of the American Chemical Society, 1961
closest-packed. The two exceptions are europium and ytterbium, which form orthorhombic dihydrides... more closest-packed. The two exceptions are europium and ytterbium, which form orthorhombic dihydrides.2 We wish to report the synthesis of a noteworthy higher hydride of ytterbium. For our investigations of rare-earth hydrogen systems in regions of high dissociation pressures (up to 65 atm.), we constructed a stainless steel high-pressure system. This consisted of an atomic hydrogen welded, 3 double-walled bomb, in which the outer chamber could be pressured with hydrogen to prevent diffusion from the inner boiiib a t the high temperatures. Accessories consisted of a 0-1000 p.s.i. Bourdon gauge and a steel reservoir of uranium hydride for pressuring the system. The ytterbium-hydrogen system was of particular interest since it seemed likely that the predicted thermodynamic stability of a trihydride phase placed it within range of attainable high pressures. The inner bomb was charged with eight grams of cleaned, 99.8yo ytterbium metal4 and first heated in vacuo. It then was allowed to absorb hydrogen a t atmospheric pressure until the composition of the hydride was YbHI.90. The hydrogen pressure in the apparatus was increased to several atmospheres and pressure-teniperaturecomposition data obtained. At a composition of YbHZ.4 the dissociation pressure was 20.9 atm. a t 312'. Upon completion of the experiments, the sample was removed from the bomb in a protective atmosphere. I t was a black, air-stable substance; a 94 mg. sample stored in air for 70 days gained less than 1 mg. Examination by powder X-ray diff raction techniques showed the presence of a f.c.c.
The Journal of Organic Chemistry, 2011
Using an intramolecular [4 þ 2] cycloaddition/rearrangement cascade of 3-(1,4-dioxaspiro[4.4]non-... more Using an intramolecular [4 þ 2] cycloaddition/rearrangement cascade of 3-(1,4-dioxaspiro[4.4]non-7-en-7-yl)-N-furan-2ylpropionamide (23) as the key step, the BCD core of the lycopodium alkaloid fawcettidine was constructed. Heating the initially formed Diels-Alder cycloadduct at 180°C results in a nitrogen-assisted ring opening followed by a deprotonation/reprotonation of the ensuing zwitterion to give a rearranged hexahydroindolinone. Our attempts to induce a related intramolecular furan Diels-Alder reaction (IMDAF) from the corresponding ketone of 23 failed to give any cycloaddition product. Instead, the only product obtained corresponded to a cyclopentenone derivative derived by isomerization of the double bond into the thermodynamically more stable R,β-position. Efforts toward construction of the final skeleton of fawcettidine by ring A closure of the rearranged cycloadduct derived from furanyl amide 23 are discussed.
Journal of the American Chemical Society, 1980
The Journal of Organic Chemistry, 1997
A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved b... more A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved by virtue of the development of highly diastereo-and enantioselective syntheses of the bottom-and top-half fragments 4 and 5 reported herein. These fragments previously served as key intermediates in Yoshii's pioneering total synthesis of (+)-tetronolide. The synthesis of the bottom-half octahydronaphthalene unit 4 features the intramolecular Diels-Alder reaction of tetraenal 20 and proceeds in 17 steps and 5-6% yield from D-glyceraldehyde pentylidene acetal 8. The synthesis of the spirotetronate fragment 5 features the highly enantioselective exo selective Diels-Alder reaction of triene 37 and chiral dienophile 25b and proceeds in 14 steps and 10% overall yield from cis-2butene-1,4-diol (38). An enantioselective synthesis of Boeckman's top-half cyclohexene fragment 6 via the exo selective Diels-Alder reaction of diene 24 and dienophile 25a was also developed, but this route was deemed too inefficient for use in a projected total synthesis of the natural product. The syntheses of 5 and 6 provide important information on the utility of chiral dienophiles 25a and 25b in organic synthesis.
ChemInform, May 19, 2010
ABSTRACT
Journal of the Chemical Society, Chemical Communications, 1987
ABSTRACT
J. Chem. Soc., Perkin Trans. 1, 1992
Attempts to form carbonyl ylides from free carbenes derived from diazirines or diazo compounds la... more Attempts to form carbonyl ylides from free carbenes derived from diazirines or diazo compounds lacking electron-withdrawing substituents resulted in azine formation or Wolff rearrangement, respectively, lodonium ylides proved to be a possible alternative to α-diazo compounds for metallocarbenoid generation, similar reactivity being observed for both systems. Studies into the rearrangement chemistry of carbonyl ylides provided a novel cyclic enol–ether synthesis via a 1,4-hydrogen shift process.
The Journal of Organic Chemistry, 1995
... 53 A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of... more ... 53 A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of Benzo-Substituted C yclopentenones Albert Padwa,* Jamal M. Kassir, Mark A. Semones,? and M. David Weingarten$ ... 1976,49, 2298. (25) Gillon. A.; Ovadia. D.; &Don. ...
Cheminform, 2002
Skip to Content. If you are seeing this message, you may be experiencing temporary network proble... more Skip to Content. If you are seeing this message, you may be experiencing temporary network problems. Please wait a few minutes and refresh the page. If the problem persists, you may wish to report it to your local Network Manager. ...
Tetrahedron Letters, 1980
ABSTRACT
Chemical and Pharmaceutical Bulletin, 1995
Angewandte Chemie International Edition, 2003
Bulletin of the Chemical Society of Japan, 1976
A Critical Review of the 1993 Literature Preceded by Two Chapters on Current Heterocyclic Topics, 1994
Journal of the American Chemical Society, 1965
Journal of the American Chemical Society, 1963
ABSTRACT
Journal of the American Chemical Society, 1963
ABSTRACT
Journal of the American Chemical Society, 1961
closest-packed. The two exceptions are europium and ytterbium, which form orthorhombic dihydrides... more closest-packed. The two exceptions are europium and ytterbium, which form orthorhombic dihydrides.2 We wish to report the synthesis of a noteworthy higher hydride of ytterbium. For our investigations of rare-earth hydrogen systems in regions of high dissociation pressures (up to 65 atm.), we constructed a stainless steel high-pressure system. This consisted of an atomic hydrogen welded, 3 double-walled bomb, in which the outer chamber could be pressured with hydrogen to prevent diffusion from the inner boiiib a t the high temperatures. Accessories consisted of a 0-1000 p.s.i. Bourdon gauge and a steel reservoir of uranium hydride for pressuring the system. The ytterbium-hydrogen system was of particular interest since it seemed likely that the predicted thermodynamic stability of a trihydride phase placed it within range of attainable high pressures. The inner bomb was charged with eight grams of cleaned, 99.8yo ytterbium metal4 and first heated in vacuo. It then was allowed to absorb hydrogen a t atmospheric pressure until the composition of the hydride was YbHI.90. The hydrogen pressure in the apparatus was increased to several atmospheres and pressure-teniperaturecomposition data obtained. At a composition of YbHZ.4 the dissociation pressure was 20.9 atm. a t 312'. Upon completion of the experiments, the sample was removed from the bomb in a protective atmosphere. I t was a black, air-stable substance; a 94 mg. sample stored in air for 70 days gained less than 1 mg. Examination by powder X-ray diff raction techniques showed the presence of a f.c.c.
The Journal of Organic Chemistry, 2011
Using an intramolecular [4 þ 2] cycloaddition/rearrangement cascade of 3-(1,4-dioxaspiro[4.4]non-... more Using an intramolecular [4 þ 2] cycloaddition/rearrangement cascade of 3-(1,4-dioxaspiro[4.4]non-7-en-7-yl)-N-furan-2ylpropionamide (23) as the key step, the BCD core of the lycopodium alkaloid fawcettidine was constructed. Heating the initially formed Diels-Alder cycloadduct at 180°C results in a nitrogen-assisted ring opening followed by a deprotonation/reprotonation of the ensuing zwitterion to give a rearranged hexahydroindolinone. Our attempts to induce a related intramolecular furan Diels-Alder reaction (IMDAF) from the corresponding ketone of 23 failed to give any cycloaddition product. Instead, the only product obtained corresponded to a cyclopentenone derivative derived by isomerization of the double bond into the thermodynamically more stable R,β-position. Efforts toward construction of the final skeleton of fawcettidine by ring A closure of the rearranged cycloadduct derived from furanyl amide 23 are discussed.
Journal of the American Chemical Society, 1980
The Journal of Organic Chemistry, 1997
A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved b... more A formal total synthesis of (+)-tetronolide, the aglycon of the tetrocarcins, has been achieved by virtue of the development of highly diastereo-and enantioselective syntheses of the bottom-and top-half fragments 4 and 5 reported herein. These fragments previously served as key intermediates in Yoshii's pioneering total synthesis of (+)-tetronolide. The synthesis of the bottom-half octahydronaphthalene unit 4 features the intramolecular Diels-Alder reaction of tetraenal 20 and proceeds in 17 steps and 5-6% yield from D-glyceraldehyde pentylidene acetal 8. The synthesis of the spirotetronate fragment 5 features the highly enantioselective exo selective Diels-Alder reaction of triene 37 and chiral dienophile 25b and proceeds in 14 steps and 10% overall yield from cis-2butene-1,4-diol (38). An enantioselective synthesis of Boeckman's top-half cyclohexene fragment 6 via the exo selective Diels-Alder reaction of diene 24 and dienophile 25a was also developed, but this route was deemed too inefficient for use in a projected total synthesis of the natural product. The syntheses of 5 and 6 provide important information on the utility of chiral dienophiles 25a and 25b in organic synthesis.
ChemInform, May 19, 2010
ABSTRACT
Journal of the Chemical Society, Chemical Communications, 1987
ABSTRACT
J. Chem. Soc., Perkin Trans. 1, 1992
Attempts to form carbonyl ylides from free carbenes derived from diazirines or diazo compounds la... more Attempts to form carbonyl ylides from free carbenes derived from diazirines or diazo compounds lacking electron-withdrawing substituents resulted in azine formation or Wolff rearrangement, respectively, lodonium ylides proved to be a possible alternative to α-diazo compounds for metallocarbenoid generation, similar reactivity being observed for both systems. Studies into the rearrangement chemistry of carbonyl ylides provided a novel cyclic enol–ether synthesis via a 1,4-hydrogen shift process.
The Journal of Organic Chemistry, 1995
... 53 A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of... more ... 53 A Tandem Cyclization-Onium Ylide Rearrangement-Cycloaddition Sequence for the Synthesis of Benzo-Substituted C yclopentenones Albert Padwa,* Jamal M. Kassir, Mark A. Semones,? and M. David Weingarten$ ... 1976,49, 2298. (25) Gillon. A.; Ovadia. D.; &Don. ...
Cheminform, 2002
Skip to Content. If you are seeing this message, you may be experiencing temporary network proble... more Skip to Content. If you are seeing this message, you may be experiencing temporary network problems. Please wait a few minutes and refresh the page. If the problem persists, you may wish to report it to your local Network Manager. ...
Tetrahedron Letters, 1980
ABSTRACT