Search results for " molecule"

- conformational preference of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

1985

Abstract The 1 H and 13 C nmr spectra of exo , exo -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d 6 or alkaline D 2 O, clearly show that it exists in a boat - chair -conformation with equatorial carboxyl groups, thus being the first case of boat - chair preference of a bicyclo[3.3.1] nonan-9-one due to the presence of exo , exo -2,4- substituents.

Front Cover: Synthesis and Unusual NMR-Spectroscopic Behavior of a Strained Bicyclic Ammonium Salt (Eur. J. Org. Chem. 10/2018)

2018

Heterocyclic rearrangements.N,N-diphenylhydrazones, oximes andO-methyloximes of 3-benzoyl-5-phenyl-1,2,4-oxadiazole

1985

The behaviour of (E)- and (Z)-N,N-diphenylhydrazones and O-Methyloximes of 3-benzoyl-5-phenyl-1,2,4-oxadiazole has been studied. When refluxed in benzene, or in dioxane-water (1:1), the (Z)-N,N-diphenylhydrazone 8Z gave the indazole 11 or the substituted semicarbazide 12, respectively. The O-methyloxime 14Z did not give any rearrangement. A criticism of the oximation reaction of 3-benzoyl-5-phenyl-1,2,4-oxadiazole is also reported.

Einführung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerüst

1987

Ausgehend von den auf verschiedenen Wegen zuganglichen Ketonen 1a–c wird die Einfuhrung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerust mit Hilfe der Selenadiazol-Methode untersucht. Dabei Konnen die hochgespannten Bicyclo-[6.1.0]nonine 2a und 2b in reiner Form isoliert werden. Masgeblich fur die Position der Dreifachbindung ist die Regioselektivitat der Ringschlusreaktion bei der Selenadiazolbildung. Introduction of a Triple Bond into the Bicyclo[6.1.0]nonane Skeleton The introduction of a triple bond into the bicyclo[6.1.0]nonane skeleton is investigated by applying the selenadiazole method to the ketones 1a–c, accessible on different pathways. The highly strained bicyclo[6.1.0]no…

ChemInform Abstract: First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis-Hillman Reaction Between Alkyl Vinyl Ketones and Aryl …

2008

Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism …

Cycloaddition of benzothiete and electron-deficient nitriles

1991

The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.

Mechanismus und Reaktionswege der Xanthenylierung an ambidenten nukleophilen Arzneistoffen

1986

Am Beispiel der ambidenten nukleophilen Arzneistoffe 4-Aminobenzolsulfonamid (3), Indometacin (7) und Phenylbutazon (10) werden Aralkylierungen mit dem SN1-aktiven Reagens Xanthydrol (1) vorgestellt. Mechanism and Reaction Path of the Xanthenylation of Ambident Nucleophilic Drugs The aralkylation of ambident nucleophilic drugs, e.g. 4-aminobenzenesulfonamide (3), indometacine (7) and phenylbutazone (10), with SN1-active xanthydrol (1) is described.

A new access to 2′-amino-substituted vinylindoles as donor-activated heterocyclic dienes and their first diels-alder reactions

1992

Abstract Reactions of the 3-acylindoles 5, 10 , and 15 with α-amino-α′-diphenylphosphinoyl-substituted carbanions gave rise to the 2′-amino-substituted 3− and 2-vinylindoles 7, 12 , and 17 by way of the isolable carbinols 6 , 11 , and 16 . The heterocyclic dienes 7 , 12 , and 17 readily underwent Diels-Alder reactions with N -phenylmaleimide.

Structure elucidation of benzopyran-2-ol in solution and in solid state following the reduction of coumarin by DIBAL-H

2001

Lactols are compounds of increasing interest in the synthesis of active pharmaceutical derivatives. Nevertheless, the product obtained by the reduction of the carbonyl group of coumarin has been described only twice, and without definition of its precise chemical structure. Since these studies, doubts have been raised about the existence of a monomeric or dimeric form. Our study has led us to conclude definitely that the single dimeric form exists and to precisely define the spectral properties of the two diastereoisomers.

ChemInform Abstract: Studies on Bicyclo[3.3.1]nonanes for Synthesis of Cyclooctenes.

2010

This paper describes a full conformational and stereochemical study of bicylo[3.3.1]nonanes, obtained from the reaction between cinnamaldehyde and 1-morpholine 1-cyclohexene. NMR data and stereochemistry were unequivocally established and assigned by two-dimensional experiments and single-crystal X-ray analysis. The crystal structure of a minor compound, 4, is reported. Cyclooctenes, which are present in natural products with biological activities, were synthesized from the bicyclononanes via the Wharton fragmentation.