The Chemistry of Sulfur Curing. III. Effects of Zinc Oxide on the Mechanism of the Reaction of Cyclohexene with Sulfur

1968 ◽  
Vol 41 (5) ◽  
pp. 1329-1338 ◽  
Author(s):  
James R. Wolfe ◽  
Thomas L. Pugh ◽  
A. Stanley Killian
Keyword(s):  
Zinc Oxide ◽  
Aluminum Hydride ◽  
Major Product ◽  
Lithium Aluminum ◽  
Chain Reaction ◽  
Radical Chain ◽  
Hydride Reduction ◽  
Cis And Trans ◽  
Radical Chain Reaction ◽  
Mechanism Of The Reaction

Abstract Reaction of cyclohexene and sulfur at 140° followed by lithium aluminum hydride reduction of the polysulfide products results in the formation of cyclohexanethiol, 2-cyclohexene-1-thiol, cis- and trans-1, 2-cyclohexanedithiol, and cyclohexyl sulfide. If zinc oxide is present during the reaction, trans-1, 2-cyclohexanedithiol is the major product. In the absence of zinc oxide, cis-1, 2-cyclohexanedithiol is the major product. It is postulated that in the absence of zinc oxide the reaction proceeds via a free radical chain involving polysulfenyl radicals accompanied by a secondary polar addition reaction of hydrosulfide products with cyclohexene. Zinc oxide when present is postulated to initiate an ionic chain reaction which, due to its greater velocity, dominates the radical chain reaction.

The Chemistry of Sulfur Curing. IV. Effects of Organic Accelerators on the Reaction of Cyclohexene with Sulfur

1968 ◽  
Vol 41 (5) ◽  
pp. 1339-1347 ◽  
Author(s):  
James R. Wolfe
Keyword(s):  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Major Product ◽  
Lithium Aluminum ◽  
Radical Mechanism ◽  
Secondary Products ◽  
Tetramethylthiuram Disulfide ◽  
Hydride Reduction ◽  
Free Radical Mechanism ◽  
Cis And Trans

Abstract Cyclohexene reacts with sulfur at 140° in the presence of zinc dimethyldithio-carbamate, tetramethylthiuram monosulfide, or tetramethylthiuram disulfide, to produce 2-cyclohexene-1-thiol as the major product after lithium aluminum hydride reduction of the polysulfide compounds. Secondary products are cis- and trans-1, 2-eyclohexanedithiol and cyclohexanethiol. Zinc dimethyldithiocarbamate is postulated to promote the reaction via an ionic mechanism as it causes more trans than cis-1, 2-cyclohexanedithiol to be formed. Tetramethylthiuram monosulfide and disulfide are postulated to promote the reaction via a free radical mechanism as they cause more cis- than trans-1, 2-cyclohexanedithiol to be formed.

Synthesis oftrans- and cis-α-damascone

1978 ◽  
Vol 56 (10) ◽  
pp. 1368-1371 ◽  
Author(s):  
Hsing-Jang Liu ◽  
Hing-Kwok Hung ◽  
George L. Mhehe ◽  
M. L. Duarte Weinberg
Keyword(s):  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Complete Recovery ◽  
Lithium Aluminum ◽  
Magnesium Bromide ◽  
Keto Ester ◽  
Keto Esters ◽  
Hydride Reduction ◽  
Cis And Trans ◽  
Cis Isomer

Se lective thioketalization of a mixture of keto esters 5 and 6 resulted in the exclusive formation of thioketal 7 and complete recovery of keto ester 6. Lithium aluminum hydride reduction of thioketal 7 followed by Moffatt oxidation of the resulting alcohol 8 gave aldehyde 10 which on treatment with a mixture of cis- and trans-1-propenyl magnesium bromide afforded trans- alcohol 11 and its cis isomer 12. Manganese dioxide oxidation of alcohol 11 followed by desulfurization gave trans α-damascone (3). Similarly, alcohol 12 was converted to cis-α-damascone (4).

Reduction of Some Alkylisoxazoles with Lithium Aluminum Hydride

1975 ◽  
Vol 53 (20) ◽  
pp. 3011-3013 ◽  
Author(s):  
A. L. Khurana ◽  
A. M. Unrau
Keyword(s):  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Major Product ◽  
Major Constituent ◽  
Lithium Aluminum ◽  
Hydride Reduction

Lithium aluminum hydride reduction of alkyl substituted isoxazoles gave a variety of products. The major constituent was identified (i.r., n.m.r., m.s.) as hydroxyethylaziridine. Specifically, reduction of 3,4,5-trimethylisoxazole gave as the major product 2,3-dimethyl-3-β-hydroxyethylaziridine. Two of the more prominent minor products were identified as 2,3-dimethyl-3-ethylaziridine and 4-amino-3-methyl-2-pentanol. The corresponding products were identified when 3,5-dimethylisoxazole was reduced with LAH.

STEROIDS: I. 12β-METHYL-12α-HYDROXYPROGESTERONE

1961 ◽  
Vol 39 (3) ◽  
pp. 548-554 ◽  
Author(s):  
George Just ◽  
R. Nagarajan
Keyword(s):  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Major Product ◽  
Lithium Aluminum ◽  
Hydride Reduction

Lithium aluminum hydride reduction of 3α,12α -diacetoxypregnan-20-one (Ia) gives as the major product pregnane-3α,12α,20β-triol (III), whereas the reduction of the corresponding dihydroxypregnanone I affords mainly the epimeric 3α,12α,20α-triol II. Triol III was transformed to 12β-methyl-12α-hydroxyprogesterone (VIII).

Synthesis and conformational assignment of cis- and trans-2-amino-1-arylcyclohexanols

1985 ◽  
Vol 63 (11) ◽  
pp. 3186-3194 ◽  
Author(s):  
Antonio Delgado ◽  
Ricardo Granados ◽  
David Mauleon ◽  
Inmaculada Soucheiron ◽  
Miguel Feliz
Keyword(s):  
Aluminum Hydride ◽  
Chair Conformation ◽  
Lithium Aluminum ◽  
Aryl Group ◽  
Conformationally Restricted ◽  
H Nmr ◽  
Hydride Reduction ◽  
Reagent Treatment ◽  
Sodium Borohydride Reduction ◽  
Cis And Trans

The synthesis of cis- and trans-2-amino-1-arylcyclohexanols 1–8, conformationally restricted analogues of the α-adrenergic drugs norephedrine 9, methoxamine 10, and isopropylmethoxamine 11, is described. trans-Aminoalcohols were obtained through reaction of epoxides 12 or 13 with isopropylamine (to afford 4 and 8) or with sodium azide followed by lithium aluminum hydride reduction (to afford 2 and 6), whereas cis-aminoalcohols 1 and 5 were obtained by condensation of 2-aminocyclohexanone hydrobromide 26 with the appropriate organometallic reagent. Treatment of 1 and 5 with acetone followed by sodium borohydride reduction gave isopropylaminoalcohols 3 and 7. Configurational and conformational assignments of aminoalcohols 1–8 have been carried out on the basis of their 1H nmr and 13C nmr data and by comparison with reference diols 18 and 30. The major or exclusive chair conformation observed for all the compounds has an equatorial aryl group.

Catalyst- and Silane- Controlled Enantioselective Hydrofunctionalization of Alkenes by Cobalt-Catalyzed Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Kousuke Ebisawa ◽  
Kana Izumi ◽  
Yuka Ooka ◽  
Hiroaki Kato ◽  
Sayori Kanazawa ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Absolute Configuration ◽  
Kinetic Resolution ◽  
Hydrogen Atom Transfer ◽  
Biologically Active ◽  
Atom Transfer ◽  
High Concentration ◽  
Chain Reaction ◽  
Radical Chain ◽  
Radical Chain Reaction

Catalytic enantioselective synthesis of tetrahydrofurans, which are found in the structures of many biologically active natural products, via a transition-metal catalyzed-hydrogen atom transfer (TM-HAT) and radical-polar crossover (RPC) mechanism is described herein. Hydroalkoxylation of non-conjugated alkenes proceeded efficiently with excellent enantioselectivity (up to 94% ee) using a suitable chiral cobalt catalyst, <i>N</i>-fluoro-2,4,6-collidinium tetrafluoroborate, and diethylsilane. Surprisingly, absolute configuration of the product was highly dependent on the steric hindrance of the silane. Slow addition of the silane, the dioxygen effect in the solvent, thermal dependency, and DFT calculation results supported the unprecedented scenario of two competing selective mechanisms. For the less-hindered diethylsilane, a high concentration of diffused carbon-centered radicals invoked diastereoenrichment of an alkylcobalt(III) intermediate by a radical chain reaction, which eventually determined the absolute configuration of the product. On the other hand, a more hindered silane resulted in less opportunity for radical chain reaction, instead facilitating enantioselective kinetic resolution during the late-stage nucleophilic displacement of the alkylcobalt(IV) intermediate.

The reaction of thionitrites with barton esters: a convenient free radical chain reaction for decarboxylative nitrosation

Tetrahedron ◽  
1999 ◽  
Vol 55 (12) ◽  
pp. 3573-3584 ◽  
Author(s):  
Pierre Girard ◽  
Nadine Guillot ◽  
William B. Motherwell ◽  
Robyn S. Hay-Motherwell ◽  
Pierre Potier
Keyword(s):  
Free Radical ◽  
Chain Reaction ◽  
Radical Chain ◽  
Free Radical Chain Reaction ◽  
Radical Chain Reaction
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