Clemmensen Reduction. XI. Fragmentation Reactions of Some 3-Acetylcycloalkanones

1995 ◽  
Vol 48 (11) ◽  
pp. 1827 ◽  
Author(s):  
KE Bailey ◽  
BR Davis
Keyword(s):  
Major Product ◽  
Unsaturated Ketone ◽  
Clemmensen Reduction ◽  
Fragmentation Reactions

Clemmensen reduction of a series of 3-acetylcycloalkanones yields, as the major product, an acyclic unsaturated ketone, the product of fragmentation. Some normal carbonyl-methylene reduction also occurs. A mechanistic rationale for the fragmentation is advanced.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

Selective reduction of aromatic alkynes catalyzed by palladium with formic acid as the hydride source

2021 ◽  
Vol 08 ◽  
Author(s):  
Suzanne Chayya ◽  
Mohammad H. El-Dakdouki ◽  
Akram Hijazi ◽  
Ghassan Younes ◽  
Ghassan Ibrahim ◽  
...  
Keyword(s):  
Formic Acid ◽  
Selective Reduction ◽  
Major Product ◽  
Transfer Hydrogenation ◽  
Attractive Alternative ◽  
Unsaturated Ketone ◽  
Partial Reduction ◽  
Reaction Parameters ◽  
Reaction Conditions ◽  
Optimized Conditions

Background: Transfer hydrogenation methods that employ non-H2 hydrogen sources have evolved as an attractive alternative for conventional hydrogenation approaches. Objective: In this study, we aimed at developing optimized conditions to induce the selective transfer hydrogenation reduction of aromatic alkynes catalyzed by PdCl2(PPh3)2 and using formic acid as the hydride source. Methods: The effect of various reaction parameters, such as the nature and amount of the catalyst, the H-donor/base couple, reaction time and temperature, and the nature of the solvent on the outcome of the alkyne reduction were investigated. Results: The reduction of the alkyne can be chemoselectively controlled by adjusting the reaction conditions. Among the tested catalysts, PdCl2(PPh3)2 was the most suitable with 2% of the catalyst being the optimal amount. While the reduction was successful in different solvents of different polarities, THF was selected as the solvent of choice. The reduction of diphenylacetylene yielded the alkene both at 50oC and 80oC. When testing the optimized conditions on the reduction of 4-phenyl-3-butyne-2-one, quantitative partial reduction to the corresponding α,β-unsaturated ketone was obtained at 50oC, while the saturated ketone was produced as the major product at 80oC. Conclusion: The chemoselective reduction of aromatic alkynes was performed successfully with complete conversion using 2% PdCl2(PPh3)2 as a catalyst, formic acid/NEt3 as the H-donor/base couple, THF as the solvent, at 50oC and 80oC.

Chemistry of the Podocarpaceae. XXII. Aspects of the chemistry of Totara-8,11,13-trien-13-ol

1969 ◽  
Vol 22 (9) ◽  
pp. 1975 ◽  
Author(s):  
RC Cambie ◽  
DR Crump ◽  
RN Duve
Keyword(s):  
Sulphuric Acid ◽  
Methyl Ether ◽  
Major Product ◽  
High Yield ◽  
Lithium Aluminium Hydride ◽  
Birch Reduction ◽  
Transannular Cyclization ◽  
Lithium Aluminium ◽  
Fragmentation Reactions

Attempts have been made to effect fragmentation reactions with bromo- tetralone systems related to 6α-bromo-13-hydroxytotara-8,11,13-trien-7- one (VII), a compound which affords a secoditerpenoid (IX) when treated with DMSO-NaHCO3. On treatment with sulphuric acid in acetone, the mono- epoxide derivative (XXVIII) of the methyl ether of the secoditerpenoid undergoes a novel aromatization to a naphthalenic aldehyde (XXXI) by successive transannular cyclization and fragmentation reactions. ��� A 7β-hydroxy configuration has been confirmed for the major product from reduction of 13-acetoxytotara-8,11,13-trien-7-one (VIII) with lithium aluminium hydride. 13-Methoxytotara-8,11,13-triene (II) has been deisopropylated and then subjected to Birch reduction in an attempt to effect a high yield conversion into (+)-podocarp-8(14)-en- 13-one (XXXVII), a potentially useful intermediate for synthesis.

Effect of a miscible solvent on the Clemmensen reduction

1963 ◽  
Vol 13 (8) ◽  
pp. 346-347
Author(s):  
G. E. Risinger ◽  
J. A. Thompson
Keyword(s):  
Clemmensen Reduction

METABOLISM OF 17α-HYDROXYPROGESTERONE-4-14C-17α-CAPROATE BY HOMOGENATES OF RAT LIVER AND HUMAN PLACENTA

1961 ◽  
Vol 36 (4) ◽  
pp. 511-519 ◽  
Author(s):  
Margaret Wiener ◽  
Charles I. Lupa ◽  
E. Jürgen Plotz
Keyword(s):  
Rat Liver ◽  
Human Placenta ◽  
Steric Hindrance ◽  
Placental Tissue ◽  
Caproic Acid ◽  
Major Product ◽  
Side Chain ◽  
Anaerobic Conditions ◽  
Prolonged Action ◽  
Long Acting

ABSTRACT 17α-hydroxyprogesterone-4-14C-17α-caproate (HPC), a long-acting progestational agent, was incubated with homogenates of rat liver and human placenta. The rat liver was found to reduce Ring A of HPC under anaerobic conditions to form allopregnane-3β,17α-diol-20-one-17α-caproate and pregnane-3β,17α-diol-20-one-17α-caproate, the allopregnane isomer being the major product. The caproic acid ester was neither removed nor altered during the incubation. Placental tissue did not attack HPC under conditions where the 20-ketone of progesterone was reduced. It is postulated that this absence of attack on the side chain is due to steric hindrance from the caproate ester, and that this may account for the prolonged action of HPC.

Synthesis of Some New Tetracyclic Pyrimidine Derivatives Using Exocyclic α,β-Unsaturated Ketone and Evaluation of Their Antitumor Activities

2016 ◽  
Vol 12 (8) ◽  
pp. 311-317
Author(s):  
Kamelia El-Mahdy
Keyword(s):  
Antitumor Activity ◽  
Spectroscopic Data ◽  
Acid Hydrazide ◽  
Chloroacetic Acid ◽  
Equimolar Amount ◽  
Unsaturated Ketone ◽  
Cyanoacetic Acid ◽  
Antitumor Activities ◽  
Pyrimidine Derivatives ◽  
Cyanoacetic Acid Hydrazide

Thiazolopyrimidine 2 was obtained from the reaction of dihydropyrimidinone with chloroacetic acid and benzaldehyde. Thiazolopyrimidine 2 containing an α,β-unsaturated ketonic function [-CH=CH-CO-] has been used as a component of Michael addition with an equimolar amount of dinucleophiles to give a series of novel tetracyclic pyrimidine derivatives. Treatment of thiazolopyrimidine 2 with uracil, aminotriazole, cyanoacetic acid hydrazide, o-phenylenediamine or diaminopyridine afforded the corresponding pyridopyrimidine, triazolopyrimidine, pyrazolone, benzodiazepine and triazepine derivative, respectively. The detailed synthesis, spectroscopic data, and antitumor activity for synthesized compounds were reported.

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