A comparative study of Jones's, Collins's and Corey's reagents in the chromium(VI) oxidation of an epimeric pair of allylic alcohols in the benzo-fused Norbornen-5-ol series

1978 ◽  
Vol 31 (5) ◽  
pp. 1113 ◽  
Author(s):  
RN Warrener ◽  
TS Lee ◽  
RA Russell ◽  
MN Paddon-Row
Keyword(s):  
Comparative Study ◽  
Manganese Dioxide ◽  
Secondary Alcohol ◽  
Quantitative Yield ◽  
Current Understanding ◽  
Allylic Alcohols ◽  
Unsaturated Ketone ◽  
Oxidizing Agents ◽  
Chromium Vi ◽  
Ketone Formation

A comparison has been made between a series of chromium(VI) oxidizing agents, as well as manganese dioxide, a bicyclic allylic secondary alcohol, the exo-ol (7), being the substrate. Jones's, Collins's and Corey's reagents gave, in each case, a mixture of products: the main reactions were epoxidation to yield (8) and (9), normal ketone formation (10), and ring-fragmentation to form the indanol (11) and the indanone (12). All reagents yielded substantial amounts of epoxide, which is rare for Collins's reagent, and unprecedented for Corey's reagent, and varying amounts (13-30 %) of ketone, while Jones's reagent alone gave significant ring-opened products. A dramatic change in product composition was observed with the epimeric endo-alcohol (13), where Jones's reagent (only one studied) yielded the related α,β,-unsaturated ketone (10) in essentially quantitative yield. A discussion of these results is presented in terms of the current understanding of the mechanism of chromium oxidations.

An Apparent Stereochemical Effect in MnO2 Oxidation of Some Allylic Alcohols

1971 ◽  
Vol 49 (18) ◽  
pp. 3038-3045 ◽  
Author(s):  
Bert Fraser-Reid ◽  
Bernard J. Carthy ◽  
N. L. Holder ◽  
Mark Yunker
Keyword(s):  
Hydrogen Bonding ◽  
Manganese Dioxide ◽  
Hydroxyl Group ◽  
Allylic Alcohols ◽  
Unsaturated Ketone ◽  
Anomeric Effect ◽  
Chair Form ◽  
Large Separation ◽  
Acid Catalyzed

3,4-Di-O-acetyl-D-xylal undergoes acid-catalyzed reaction with ethanol to give the anomeric mixture of ethyl 2,3-dideoxy-4-O-acetyl-D-glycero-pent-2-enopyranosides which can be separated after deacetylation. The α-D anomer 1 is readily oxidized by manganese dioxide to the α,β-unsaturated ketone but the β-D anomer 2 is inert. Thorough investigation of the 100 and 220 MHz n.m.r. spectra of 1 and 2, their acetates, and dinitrobenzoates indicates that each exists conformationally pure in the half-chair form having the benefit of the anomeric effect. Hence in the oxidizable anomer 1 the C-4 allylic hydroxyl group is pseudo-equatorial; in the unoxidizable one it is pseudoaxial. Hydrogen bonding does not appear to be the reason for failure of 2 to oxidize.The ethoxy groups of 1 and 2 are found to be ABX3 system with unusually large separation for the AB protons.

scholarly journals Efficient Solvent-free Oxidation of Benzylic and Aromatic Allylic Alcohols and Biaryl Acyloins by Manganese Dioxide and Barium Manganate

1999 ◽  
Vol 23 (3) ◽  
pp. 236-237
Author(s):  
Habib Firouzabadi ◽  
Babak Karimi ◽  
Mohammad Abbassi
Keyword(s):  
Manganese Dioxide ◽  
Solvent Free ◽  
Allylic Alcohols ◽  
Solvent Free Conditions ◽  
Free Oxidation

Active manganese dioxide and commercially available barium manganate are used for the efficient oxidation of benzylic and aromatic allylic alcohols and biaryl acyloins under solvent-free conditions.

The Burke Synthesis of ( + )-Didemniserinolipid B

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
First Generation ◽  
Secondary Alcohol ◽  
Unsaturated Ester ◽  
Unsaturated Ketone ◽  
Grubbs Catalyst ◽  
University Of Wisconsin ◽  
Set Up ◽  
Open Face ◽  
Vinyl Group ◽  
The University

The sulfate ( + )-didemniserinolipid B 3, isolated from the tunicate Didemnum sp, has an intriguing spiroether core. A key step in the synthesis of 3 reported (Organic Lett. 2007, 9, 5357) by Steven D. Burke of the University of Wisconsin was the selective ring-closing metathesis of 1 to 2. The diol 6 that was used to prepare the ketal 1 was readily prepared from the inexpensive D-mannitol 4. Many other applications can be envisioned for the enantiomerically-pure diol 6 and for the monoacetate and bis acetate that are precursors to it. To set up the metathesis, the β, γ-unsaturated ketone 10 was needed. To this end, the keto phosphonate derived from the addition of the phosphonate anion 8 to the lactone 7 was condensed with phenyl acetaldehyde 9. The derived enone 10 was a 5:1 mixture of β, γ- and α, β-regioisomers. The diol 6 is C2 -symmetrical, but formation of the ketal 1 dissolved the symmetry, with one terminal vinyl group directed toward the styrene double bond, and the other directed away from it. On exposure to the first generation Grubbs catalyst, ring formation proceeded efficiently, to give 2. Williamson coupling with the serine-derived alcohol 11 then gave 12. To establish the secondary alcohol of 13 and so of 3, the more electron rich alkene of 12 was selectively epoxidized, from the more open face. Diaxial opening with hydride then gave 13. With 13 in hand, another challenge of selectivity emerged. The plan had been to attach the ester-bearing sidechain to 13 using alkene metathesis, then hydrogenate. As the side-chain of 3 contained an additional alkene, this had to be present in masked form. To this end, the α-phenylselenyl ester 14 was prepared. Alkene metathesis with 13 proceeded smoothly, this time using the second generation Grubbs catalyst. The unwanted alkene was then removed by reduction with diimide, and the selenide was oxidized to deliver the α, β-unsaturated ester.

Comparative study of oxidation by chromium(V) and chromium(VI)

1996 ◽  
pp. 1607 ◽  
Author(s):  
Sandra Signorella ◽  
Marcela Rizzotto ◽  
Ver�nica Daier ◽  
Mar�a I. Frascaroli ◽  
Claudia Palopoli ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chromium Vi

Bicyclisch verbrückte Cyclopentadienylanionen: 4,8-Etheno-/Ethano-2,4,6,8-tetrahydro-s-indacen-dianion / Bicyclically Bridged Cyclopentadienyl Anions: 4,8-Etheno-/Ethano-2,4,6,8-tetrahydro-s-indacene Dianion

1990 ◽  
Vol 45 (3) ◽  
pp. 329-343 ◽  
Author(s):  
Hermann Atzkern ◽  
Frank H. Köhler ◽  
Reinhard Müller
Keyword(s):  
Comparative Study ◽  
Quantitative Yield ◽  
Methylene Groups ◽  
Leaving Groups

Two cyclopentadienes have been linked in a stereochemically rigid arrangement such that the cyclopentadienes are not coplanar. The key intermediates in the synthesis were tetrakis(methylene)bicyclo[2.2.2]oct-2-ene (12) or -octane (14). The access to 12 and 14 was investigated in a comparative study including nine different precursors which were expected to lead to the methylene groups by elimination of HX. The best results were obtained with X = mesylate with overall yields of 52% for 12 in three steps and 42% for 14 in four steps. Other leaving groups facilitated the procedures, but more steps were required or the yield was lower. During these studies 21 tetrasubstituted bicyclo[2.2.2]oct-2-enes and -octanes were obtained and characterized, in particular by the δ(13C) and in most cases the 1J(13C –1H) and δ(1H) values. Both 12 and 14 added CBr2 selectively in that only isomers with two dibromo-(vinyl)cyclopropane fragments per molecule were obtained. One isomer showing C2-symmetry could be isolated from the mixture. After reaction with methyllithium the corresponding linked cyclopentadienes with unsaturated (20) or saturated bridge (21) were obtained and fully characterized. Metallation of 20 and 21 gave the title dianions in quantitative yield.

scholarly journals Comparative Study of Two Oxidizing Agents, Chloramine T and Iodo-Gen®, for the Radiolabeling of β-CIT with Iodine-131: Relevance for Parkinson’s Disease

2019 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
Ana R. Durante ◽  
Danielle V. Sobral ◽  
Ana C. Miranda ◽  
Érika V. de Almeida ◽  
Leonardo L. Fuscaldi ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Comparative Study ◽  
Radiochemical Yield ◽  
Substantia Nigra Pars Compacta ◽  
Oxidizing Agent ◽  
Oxidizing Agents ◽  
Tropane Derivatives ◽  
Chloramine T ◽  
Iodine 131

Parkinson’s disease (PD) is a neurodegenerative disease characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta, leading to alteration of the integrity of dopaminergic transporters (DATs). In recent years, some radiopharmaceuticals have been used in the clinic to evaluate the integrity of DATs. These include tropane derivatives such as radiolabeled β-CIT and FP-CIT with iodine-123 (123I), and TRODAT-1 with metastable technetium-99 (99mTc). Radiolabeling of β-CIT with radioactive iodine is based on electrophilic radioiodination using oxidizing agents, such as Chloramine T or Iodo-Gen®. For the first time, the present work performed a comparative study of the radiolabeling of β-CIT with iodine-131 (131I), using either Chloramine T or Iodo-Gen® as oxidizing agents, in order to improve the radiolabeling process of β-CIT and to choose the most advantageous oxidizing agent to be used in nuclear medicine. Both radiolabeling methods were similar and resulted in high radiochemical yield (> 95%), with suitable 131I-β-CIT stability up to 72 h. Although Chloramine T is a strong oxidizing agent, it was as effective as Iodo-Gen® for β-CIT radiolabeling with 131I, with the advantage of briefer reaction time and solubility in aqueous medium.

Sign in / Sign up

Export Citation Format

Share Document