Search results for "Pentane"

CCDC 1519225: Experimental Crystal Structure Determination

2017

Related Article: Sabrina Antonello, Tiziano Dainese, Fangfang Pan, Kari Rissanen, Flavio Maran|2017|J.Am.Chem.Soc.|139|4168|doi:10.1021/jacs.7b00568

Solution and fluorous phase synthesis of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives

2008

An efficient protocol for the preparation of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives was developed. 2,2-Difluro-4-phenyl-3-butenoic acid 6 was used as substrate for the preparation of the starting vinyl difluoro imino esters 8. The key steps of this methodology rely on the chemo- and diastereoselective addition of allylzinc bromides over the iminic functionality of 8 and subsequent RCM reaction. This synthetic sequence was successfully applied to fluorous synthesis.

1984

Sedimentation coefficients of S of polystyrene covering a broad range of molecular weights M, are measured in toluene and 2-butanone in the semidilute regime. The results are compared with literature data using a plot of S · NA · η/(1 − νρ) = M · η/f versus concentration c, allowing experiments in different solvents of different density ρ and viscosity η to be compared (ν: partial specific volume of polymer; f: friction coefficient; NA: Avogadro number). According to scaling theory for concentrations higher than a critical concentration c, linear plots are to be expected. This is true for the theta-solvent cyclohexane, but for the theta-solvent cyclopentane as well as for the thermodynamica…

Synthesis of Highly Functionalized Cyclopentanes as Precursors of Hydroxylated Azidocarbonucleosides

2009

Regio- and stereoisomers of functionalized azido amino alcohols with a cyclopentane skeleton were synthesized in enantiomerically pure forms. Enzymatic ring cleavage of racemic 2-azabicyclo[2.2.1]hept-5-en-3-one gave the corresponding amino acid and one enantiomer of the lactam stereospecifically. These were protected by esterification and carbamoylation, and then epoxidized. The resulting oxiranes underwent cleavage by sodium azide with complementary stereoselectivities. The regioisomeric products were easily separated by crystallization or column chromatography.

Cyclic fatty acid monomers : synthesis and characterization of methyl w-(2-alkylcyclopentyl) alkenoates and alkanoates

1988

Abstract Some 1,2-disubstituted cyclopentanes were synthesized. These were methyl 9-(2-butyl-cyclopentyl)-8-nonenoate, methyl 7-(2-hexyl-cyclopentyl)-6-heptenoate and methyl 5-(2-octyl-cyclopentyl)-4-pentenoate and their corresponding alkanoates. The synthesis involved a Michael addition of alkylmagnesium bromide to an unsaturated cyclic ester. The resulting cis and trans ethyl 2-alkylcyclopentane carboxylate were further converted to the alcohols then to the aldehydes. The aldehydes were condensed with the ylide derived from the (ω-carboxyalkyl)-triphenylphosphonium bromide and methylsulfinylmethide in DMSO to give unsaturated C18 cyclic fatty acid monomers. These cyclic fatty acids were f…

High Enantiocontrol in the Intramolecular Cyclopropanation of Diazo Ketones Catalyzed by Dirhodium(II) Complexes with Ortho-Metalated Aryl Phosphine …

2001

[reaction: see text]. Chiral dirhodium(II) complexes, Rh2(O2CCF3)2(PC)2, [PCH = (p-CH3C6H4)3P, (m-CH3C6H4)3P], provide an excellent yield and a high enantiocontrol in the cyclopropanation of alpha-diazo ketones with gamma and delta double bonds. The ee values are significantly dependent on the solvent used; the best results are obtained using pentane.

ChemInform Abstract: Solution and Fluorous Phase Synthesis of β,β-Difluorinated 1-Amino-1-cyclopentane Carboxylic Acid Derivatives.

2009

An efficient protocol for the preparation of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives was developed. 2,2-Difluro-4-phenyl-3-butenoic acid 6 was used as substrate for the preparation of the starting vinyl difluoro imino esters 8. The key steps of this methodology rely on the chemo- and diastereoselective addition of allylzinc bromides over the iminic functionality of 8 and subsequent RCM reaction. This synthetic sequence was successfully applied to fluorous synthesis.

Back Cover: Chemoselective, Substrate-directed Fluorination of Functionalized Cyclopentane β-Amino Acids (Chem. Asian J. 23/2016)

2016

An Insight into Substrate-Dependent Fluorination of some Highly Substituted Alicyclic Scaffolds

2017

The substrate-dependent fluorination of some highly-functionalized cyclopentane derivatives with multiple chiral centers has been investigated. The key steps of the stereocontrolled syntheses are the oxidative cleavage of the ring carbon–carbon double bond of readily available diexo or diendo norbornene β-amino acid derivatives followed by transformation of the resulted dialdehyde stereoisomers by reduction. Finally, substrate-directable chemodifferentiation of different types of hydroxy groups under fluorination procedures gave various densely functionalized alicyclic derivatives or heterocycles.

Differentiation of isomeric cyclic diamides by electron impact mass spectra

1976

The behaviour under electron impact of two series of isomeric cyclopentane- and cyclohexane-1, 2- and -1, 3-dicarboxylic acid dipiperidides was studied. Diagnostic fragmentation pathways were found to differentiate the isomeric diamides. Additional evidence was obtained from the metastable transitions.