Exploiting the Facile Release of Trifluoroacetate for the α-Methylenation of the Sterically Hindered Carbonyl Groups on (+)-Sclareolide and (−)-Eburnamonine

2011 ◽  
Vol 76 (10) ◽  
pp. 3676-3683 ◽  
Author(s):  
Mark V. Riofski ◽  
Jinu P. John ◽  
Mary M. Zheng ◽  
Julia Kirshner ◽  
David A. Colby
Keyword(s):  
Carbonyl Groups ◽  
Sterically Hindered

[N,N′-Bis(2,6-diisopropylphenyl)acenaphthene-1,2-diimine-1κ2N,N′]heptacarbonyl-1κC,2κ3C,3κ3C-di-μ3-tellurido-triiiron(II)(2Fe—Fe)

2012 ◽  
Vol 68 (11) ◽  
pp. m320-m322 ◽  
Author(s):  
Dmitry A. Piryazev ◽  
Mikhail A. Ogienko ◽  
Alexander V. Virovets ◽  
Nikolay A. Pushkarevsky ◽  
Sergey N. Konchenko
Keyword(s):  
Electron Transfer ◽  
Title Complex ◽  
Cluster Core ◽  
Carbonyl Groups ◽  
Asymmetric Unit ◽  
Bond Lengths ◽  
Low Level ◽  
Redox Active ◽  
Sterically Hindered

The sterically hindered title complex, [Fe3Te2(C36H40N2)(CO)7], was obtained by substitution of two carbonyl groups in the [Fe3(μ3-Te)2(CO)9] cluster by the bulky redox-activeN,N′-bis(2,6-diisopropylphenyl)acenaphthene-1,2-diimine (dpp-BIAN) ligand. The asymmetric unit contains two molecules of the same geometry. The C=N bond lengths in dpp-BIAN indicate a rather low level of electron transfer from the cluster core to the dpp-BIAN ligand.

Methylsteroids. V. The faciliation of hydrolysis of sterically hindered acetoxy groups by carbonyl groups in the Lanosterol series

1958 ◽  
Vol 11 (4) ◽  
pp. 546 ◽  
Author(s):  
CS Barnes
Keyword(s):  
Acetoxy Group ◽  
Carbonyl Groups ◽  
Mild Conditions ◽  
Basic Hydrolysis ◽  
Sterically Hindered ◽  
Hydrolysis Of

The facilitation of basic hydrolysis of sterioally hindered acetoxy groups has been ex mined among the lanosterol oxo derivatives. It is found that an llp-acetoxyl may be hydrolysed under mild conditions in the presence of a 7-oxo group or more easily when a 3,7-dioxo grouping is present. The 7α-acetoxy group is resistant to basic hydrolysis except in the presence of a 3- or 11-oxo group. Possible reasons for these effects are discussed.

Pyrolysis of aryl azides. IV. Neighbouring group effects by ortho carbonyl groups

1977 ◽  
Vol 30 (12) ◽  
pp. 2669 ◽  
Author(s):  
LK Dyall
Keyword(s):  
Carbonyl Groups ◽  
Aryl Azides ◽  
Phenyl Azide ◽  
Sterically Hindered ◽  
Group Effects

The question of the mechanism by which ortho carbonyl groups enhance the rate of pyrolysis of aryl azides is examined. Rate measurements on sterically hindered 1-(2-azidophenyl)ethan-1-ones are consistent with the pericyclic mechanism proposed by Dyall and Kemp1 but not with the intramolecular 1,3-dipolar addition route put forward by Hall, Behr and Reed.2 A definitive test of mechanism is also provided by 1- azidoanthraquinone and 1-(2-azidophenyl)-2,2-dimethylpropan-1-for both of which the formation of a 1,3-dipolar adduct is precluded on steric grounds but the pericyclic process is not. At 393.2 K, these two azides pyrolyse 7385 and 61.7 times faster than phenyl azide, respectively.

Chemical and orientational imaging of polymeric samples

1994 ◽  
Vol 52 ◽  
pp. 68-69
Author(s):  
H. Ade ◽  
B. Hsiao ◽  
G. Mitchell ◽  
E. Rightor ◽  
A. P. Smith ◽  
...  
Keyword(s):  
Ethylene Terephthalate ◽  
National Laboratory ◽  
Brookhaven National Laboratory ◽  
Carbonyl Groups ◽  
Aromatic Rings ◽  
Edge Structure ◽  
X Ray ◽  
Scanning Transmission ◽  
Polymeric Samples ◽  
X Ray Absorption

We have used the Scanning Transmission X-ray Microscope at beamline X1A (X1-STXM) at Brookhaven National Laboratory (BNL) to acquire high resolution, chemical and orientation sensitive images of polymeric samples as well as point spectra from 0.1 μm areas. This sensitivity is achieved by exploiting the X-ray Absorption Near Edge Structure (XANES) of the carbon K edge. One of the most illustrative example of the chemical sensitivity achievable is provided by images of a polycarbonate/pol(ethylene terephthalate) (70/30 PC/PET) blend. Contrast reversal at high overall contrast is observed between images acquired at 285.36 and 285.69 eV (Fig. 1). Contrast in these images is achieved by exploring subtle differences between resonances associated with the π bonds (sp hybridization) of the aromatic groups of each polymer. PET has a split peak associated with these aromatic groups, due to the proximity of its carbonyl groups to its aromatic rings, whereas PC has only a single peak.

Tandem Carbon-Radical Peroxidation−Addition to Carbonyl Groups Reaction. A New Synthesis of Steroidal β-Peroxy Lactones

1996 ◽  
Vol 61 (26) ◽  
pp. 9635-9635
Author(s):  
Alicia Boto ◽  
Rosendo Hernández ◽  
Ernesto Suárez ◽  
Carmen Betancor ◽  
María S. Rodríguez
Keyword(s):  
Carbonyl Groups ◽  
New Synthesis

Nickel-Catalyzed Regioselective Hydroalkylation of 1,3-Dienes with Hydrazones

2019 ◽  
Author(s):  
Leiyang Lv ◽  
Dianhu Zhu ◽  
Zihang Qiu ◽  
Jianbin Li ◽  
Chao-Jun Li
Keyword(s):  
Catalytic Method ◽  
Unsaturated Hydrocarbons ◽  
Carbon Nucleophiles ◽  
Aryl Aldehydes ◽  
Aldehydes And Ketones ◽  
Sterically Hindered

Hydroalkylation of unsaturated hydrocarbons with unstablized carbon nucleophiles is difficult and remains a major challenge. The disclosed examples so far mainly focused on the involvement of heteroatom and/or stabilized carbon nucleophiles as efficient reaction partners. Reported here is an unprecedented regioselective nickel-catalyzed hydroalkylation of 1,3-dienes with hydrazones, generated in situ from abundant aryl aldehydes and ketones and acted as both the sources of unstabilized carbanions and hydride. With this strategy, both terminal and sterically hindered internal dienes are hydroalkylated efficiently in a highly selective manner, thus providing a novel and reliable catalytic method to construct challenging C(sp3)-C(sp3) bonds.

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

A comment on the effect of carbonyl groups - on the light-induced reversion of groundwood pulp

1990 ◽  
Vol 5 (4) ◽  
pp. 159-160 ◽  
Author(s):  
Monica Ek ◽  
Helena Lennholm ◽  
Tommy Iversen
Keyword(s):  
Carbonyl Groups
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