Aryne Chemistry of Podocarpic Acid Derivatives

1994 ◽  
Vol 47 (8) ◽  
pp. 1483 ◽  
Author(s):  
RC Cambie ◽  
PI Higgs ◽  
PS Rutledge ◽  
PD Woodgate
Keyword(s):  
Anthranilic Acid ◽  
Liquid Ammonia ◽  
Oxidative Cleavage ◽  
High Yield ◽  
Amino Compound ◽  
Bromo Compound

The anthranilic acid (2), a key intermediate for the generation of an aryne at C13 of podocarpic acid derivatives, was synthesized from the 14-amino compound (5) which in turn was generated regiospecifically in high yield by treatment of the 13-bromo compound (25) with sodamide in liquid ammonia. The amine was converted into the anthranilic acid by two separate routes: firstly by directed lithiation and trapping of the lithium species with a CO2 moiety, and secondly by oxidative cleavage of an isatin fused across positions 13 and 14.

New Route to Branched-chain Aminodeoxy Sugars by Reaction of Ketoses with Acetonitrile. Synthesis of Methyl 3-C-2′-Aminoethyl-2-deoxy-α-D-arabino-hexopyranoside

1974 ◽  
Vol 52 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Alex Rosenthal ◽  
G. Schöllnhammer
Keyword(s):  
Catalytic Hydrogenation ◽  
Liquid Ammonia ◽  
High Yield ◽  
Lithium Amide ◽  
Branched Chain

Addition of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose (1) to acetonitrile in liquid ammonia at −50 to −60° in the presence of lithium amide gave, in high yield, crystalline methyl 4,6-O-benzylidene-3-C-cyanomethyl-2-deoxy-α-D-arabino-hexopyranoside (2) exclusively. The proof of structure 2 is described. Debenzylidenation of 2 afforded the branched-chain cyano glycoside 3. Compound 3 was converted into its 3,4,6-tri-O-acetate (8) and 4,6-di-O-p-nitrobenzoate (9) derivatives. Catalytic hydrogenation of 3 over rhodium on alumina yielded methyl 3-C-2′-aminoethyl-2-deoxy-α-D-arabino-hexopyranoside which was characterized as its N-2,4-dinitrophenyl derivative (7).

Designing Stability into Thermally Reactive Plumbylenes

2018 ◽  
Author(s):  
Goran Bacic ◽  
David Zanders ◽  
Anjana Devi ◽  
Sean Barry
Keyword(s):  
Structural Analysis ◽  
Vapour Pressure ◽  
Room Temperature ◽  
Vapour Deposition ◽  
Thermal Characterization ◽  
Oxidative Cleavage ◽  
High Yield ◽  
Thermal Window ◽  
The Stability

We complete the picture of thermally stable and volatile <i>N-</i>heterocyclic metallylenes with the synthesis, structural analysis, and thermal characterization of <i>rac</i>-<i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylbutane-2,3-diamido lead(II) (<b>1Pb</b>). Transamination of bis[bis(trimethylsilyl)amido] lead(II) with the free diamino ligand yields <b>1Pb</b> in high yield, whereas salt-metathesis leads to oxidative cleavage of the butane backbone and production of acetaldehyde-<i>tert-</i>butylimine. <b>1Pb</b> itself undergoes [2+2+1] cycloreversion at 150 °C to the same imine, but with a vapour pressure of 1 Torr at 94 °C a wide thermal window is available for use as a vapour deposition precursor.<div><br></div><div>We contrast this with the the extreme instability of its sisters <i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylethane-2,3-diamido lead(II) (<b>2Pb</b>) and <i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylethylene-2,3-diamido lead(II) (<b>3Pb</b>), which both reductively eliminate Pb(0) at or below room temperature. This is also in start contrast to the stability of the lighter Si, Ge and Sn congeners.</div>

Annulations of Podocarpic Acid Derivatives via an Aryne Intermediate

1994 ◽  
Vol 47 (10) ◽  
pp. 1815 ◽  
Author(s):  
RC Cambie ◽  
PI Higgs ◽  
PS Rutledge ◽  
PD Woodgate
Keyword(s):  
Convenient Method ◽  
Anthranilic Acid ◽  
High Yield ◽  
Substituted Furans

The cycloaddition of substituted furans to the diterpenoid aryne (39), generated by in situ diazotization of the anthranilic acid (1) followed by cleavage of the annulated 1,4- epoxydecahydrochrysenes, provides a convenient method for the preparation in high yield of the previously unknown 1-substituted octahydrochrysen-4-ols. Use of 1,3-dipoles under the same procedure, or under a modified procedure involving pre-isolation of the diazonium tetrafluoroborate salt (9), gave novel annulated heterocyclic products directly. Attempted [2+2] cycloadditions of electron-rich alkenes to the diterpenoid aryne (39) were largely unsuccessful but reaction with 1,1-dimethoxyethene by using in situ diazotization gave a product derived from an initial [2+2] cycloaddition.

Regioselective and regiospecific Di-π-methane rearrangements. Photoisomerization of 9-substituted 9,10-Dihydro-9,10-ethenoanthracenes

1976 ◽  
Vol 29 (5) ◽  
pp. 1005 ◽  
Author(s):  
RG Paddick ◽  
KE Richards ◽  
GJ Wright
Keyword(s):  
Hydrogen Bonding ◽  
Carbonyl Group ◽  
Amino Compound ◽  
Bromo Compound

The di-p-methane photoisomerization of a series of 9-substituted dimethyl 9,10-dihydro-9,10- ethenoanthracene-ll,12-dicarboxylates has been investigated. The bromo compound (13) rearranges regiospecifically to give 4b-bromo-4b,8b,8c,8d-tetrahydrodibenzo[a,f]cyclopropa[cd] pentalene-8c,8d- dicarboxylate (19) whereas the amine (16) rearranges regiospecifically via the 8b-amino compound which further rearranges via an imine to give the keto diester (12). Rearrangement of the acetamido compound (17) gave the 4b-isomer (22) (60%), the keto diester (12) (25 %) and a cyclooctatetraene (28) (15%), while the methoxy and ethoxy compounds (14) and (15) gave the 4b-isomers (20) and (21) (85%) and the keto diester (11) derived from the 8b-isomer. Both the 4b- and 8b-isomers (23) and (27), (65 %) and (35 %), were isolated when the methyl ethenoanthracene (18) was photolysed. The rearrangement of these compounds is explained in terms of the electronegativity and hydrogen bonding ability of the 9-substituent. The more electronegative the substituent the more the 4b-isomer is favoured while hydrogen bonding favours the 8b-isomer. Photoisomerization of the monoesters (29), (31) and (32) confirms the importance of odd-electron stabilization by an adjacent methoxy- carbonyl group in determining the direction of the rearrangement.

Reduction of trichloromethylcarbinols. Hydrogenolysis of phenyl(trichloromethyl)carbinol and 1,1,1-trichloro-2-hydroxy-6-methyl-4- heptanone on metal surfaces

1969 ◽  
Vol 47 (9) ◽  
pp. 1521-1527 ◽  
Author(s):  
Eberhard Kiehlmann ◽  
Robert J. Bianchi ◽  
Wilkins Reeve
Keyword(s):  
Acidic Medium ◽  
Liquid Ammonia ◽  
High Yield ◽  
Main Reaction ◽  
Reaction Products ◽  
Large Excess ◽  
Reflux Time ◽  
Phenethyl Alcohol ◽  
Trichloromethyl Group ◽  
Sole Product

Reduction with zinc in neutral or acidic medium or catalytic hydrogenation of phenyl(trichloromethyl)-carbinol (1) gives β,β-dichlorostyrene (2), β-chlorostyrene (3), and phenyl(dichloromethyl)carbinol (4). β,β-Dichlorostyrene is the sole product of reduction of phenyl(trichloromethyl)carbinyl methyl ether with zinc and acetic acid. Lithium in liquid ammonia reduces the trichloromethyl group of 1 to give α-phenethyl alcohol (5) in low yield; acetophenone and β-phenethyl alcohol have been identified as byproducts of this reaction.Clemmensen reduction of 1,1,1-trichloro-2-hydroxy-6-methyl-4-heptanone (6) does not yield the expected 1,1,1-trichloro-6-methyl-2-heptanol; instead, 1,1-dichloro-6-methyl-1-hepten-4-one (7) and 1,1-dichloro-6-methyl-l-heptene (8) are formed as the main reaction products. Long reflux time, efficient stirring, and the employment of a large excess of amalgamated zinc and concentrated hydrochloric acid favor the formation of 8 while 7 is obtained in high yield when sulfuric acid is used instead of hydrochloric acid.A mechanism for the reduction of trichloromethylcarbinols (1 and 6) with zinc has been proposed, 7 being postulated as an intermediate in the formation of 8.

Stereoselective Total Synthesis of Copa and Ylango Sesquiterpenoids: (+)-Copacamphor, (+)-Copaborneol, (+)-Copaisoborneol, (−)-Ylangocamphor, (−)-Ylangoborneol, (−)-Ylangoisoborneol

1975 ◽  
Vol 53 (19) ◽  
pp. 2838-2848 ◽  
Author(s):  
Edward Piers ◽  
Ronald W. Britton ◽  
M. Bert Geraghty ◽  
Robert J. Keziere ◽  
Fusao Kido
Keyword(s):  
Total Synthesis ◽  
Liquid Ammonia ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
High Yield ◽  
Lithium Aluminum ◽  
Alkylation Product ◽  
Intramolecular Alkylation ◽  
Enolate Anion ◽  
Stereoselective Syntheses

Efficient, stereoselective syntheses of the tricyclic sesquiterpenoids (+)-copacamphor (3), (+)-copaborneol (4), (+)-copaisoborneol (5), (−)-ylangocamphor (6), (−)-ylangoborneol (7), and (−)-ylangoisoborneol (8) are described. Conversion of the keto acetate 9 (previously synthesized from the dione 1) into the keto tosylate 17 was accomplished via an eight-step sequence. Intramolecular alkylation of 17 afforded, in high yield, (+)-copacamphor (3), which had previously been converted into the corresponding alcohols 4 and 5 by Kolbe-Haugwitz and Westfelt. Alkylation of the enolate anion of the bicyclic dione 2 with 2-bromopropane in hexamethylphosphoramide gave mainly the O-alkylation product 19. Conversion of 19 into the keto mesylate 29 was carried out in 5 synthetic steps. Intramolecular alkylation of 29 afforded (−)-ylangocamphor (6). Reduction of the latter with calcium in liquid ammonia gave (−)-ylangoborneol (7), while reduction with lithium aluminum hydride yielded (−)-ylangoisoborneol (8).

Designing Stability into Thermally Reactive Plumbylenes

2018 ◽  
Author(s):  
Goran Bacic ◽  
David Zanders ◽  
Anjana Devi ◽  
Sean Barry
Keyword(s):  
Structural Analysis ◽  
Vapour Pressure ◽  
Room Temperature ◽  
Vapour Deposition ◽  
Thermal Characterization ◽  
Oxidative Cleavage ◽  
High Yield ◽  
Thermal Window ◽  
The Stability

We complete the picture of thermally stable and volatile <i>N-</i>heterocyclic metallylenes with the synthesis, structural analysis, and thermal characterization of <i>rac</i>-<i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylbutane-2,3-diamido lead(II) (<b>1Pb</b>). Transamination of bis[bis(trimethylsilyl)amido] lead(II) with the free diamino ligand yields <b>1Pb</b> in high yield, whereas salt-metathesis leads to oxidative cleavage of the butane backbone and production of acetaldehyde-<i>tert-</i>butylimine. <b>1Pb</b> itself undergoes [2+2+1] cycloreversion at 150 °C to the same imine, but with a vapour pressure of 1 Torr at 94 °C a wide thermal window is available for use as a vapour deposition precursor.<div><br></div><div>We contrast this with the the extreme instability of its sisters <i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylethane-2,3-diamido lead(II) (<b>2Pb</b>) and <i>N</i><sup>2</sup>,<i>N</i><sup>3</sup>-di-<i>tert</i>-butylethylene-2,3-diamido lead(II) (<b>3Pb</b>), which both reductively eliminate Pb(0) at or below room temperature. This is also in start contrast to the stability of the lighter Si, Ge and Sn congeners.</div>

Quality films from carbon fiber evaporation for thorough coverage of TEM grids

1988 ◽  
Vol 46 ◽  
pp. 418-419
Author(s):  
N. Tempel ◽  
M. C. Ledbetter
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Carbon Films ◽  
Low Noise ◽  
Vacuum Evaporation ◽  
High Yield ◽  
Good Adhesion ◽  
Noise Structure ◽  
Resolution Electron ◽  
Carbon Foils

Carbon films have been a support of choice for high resolution electron microscopy since the introduction of vacuum evaporation of carbon. The desirable qualities of carbon films and methods of producing them has been extensively reviewed. It is difficult to get a high yield of grids by many of these methods, especially if virtually all of the windows must be covered with a tightly bonded, quality film of predictable thickness. We report here a method for producing carbon foils designed to maximize these attributes: 1) coverage of virtually all grid windows, 2) freedom from holes, wrinkles or folds, 3) good adhesion between film and grid, 4) uniformity of film and low noise structure, 5) predictability of film thickness, and 6) reproducibility.Our method utilizes vacuum evaporation of carbon from a fiber onto celloidin film and grid bars, adhesion of the film complex to the grid by carbon-carbon contact, and removal of the celloidin by acetone dissolution. Materials must be of high purity, and cleanliness must be rigorously maintained.

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