Letters in Organic Chemistry, Volume 2, No. 2, 2005
Contents
Recent Developments in Palladium-Catalyzed Coupling Reactions Pp.113-117
Pierre
van de Weghe
Stem Cells Differentiation: Organic Chemistry is Back Pp.118-123
G.
Zanoni and A. Vadala
Letters in Organic Chemistry
High-Yielding Synthesis of 3-Alkoxycarbonyl- and
3-Carboxamido-3-tropene Derivatives in Homogeneous Carbonylation Reactions of
3-Iodo-2-tropene Pp.124-127
Laszlo
Horvath, Zoltan Berente and Laszlo Kollar
Highly Diastereoselective Epoxidation of
α,β-Unsaturated Carbonyl Compounds Using Sodium Peroxide Pp.128-131
Valluru
Krishna Reddy, Buchammagari Haritha and Mitsuji Yamashita
Stereoselectivity in the Paternò-Büchi Reaction on
Chiral Allylic Alcohols, for A Discussion of the Hydroxy Directing Effect Pp.132-135
Maurizio
D’Auria, Lucia Emanuele and Rocco Racioppi
A Very Short and Efficient Synthesis of Preclamol Pp.136-138
Arnault
de Filippis, Domingo Gomez Pardo and Janine Cossy
Brown Selectivity Disobedience of Hyperdeaminative
Friedel-Crafts Benzylation: Electrophilic Aromatic Substitutions via
Hyperdeaminatively Generated Benzyl Carbocations Pp.139-144
R.W.
Darbeau, L.M. Siso, G.A. Trahan and R.S. Nolan
Lanthanide-Catalysed Cross-Cannizzaro Reduction of
Aromatic Aldehydes with Formaldehyde Pp.145-147
Xiaogen
Yang, Jianping Guo and Gang Zou
Influence of Homoallylic Fluorine Atoms on the
Regioselectivity of the Wacker Reaction Pp.148-150
J.
Guidotti, M. Tordeux, J.-C. Blazejewski and C. Wakselman
Rapid and Selective Acetalization of Aldehydes Using
Anhydrous Copper Sulfate Supported on Silica Gel (CuSO4 / SiO2)
Under Microwave Irradiation in Solvent-Free Conditions Pp.151-155
Firouz
Matloubi Moghaddam, Afsaneh Arefi Oskoui and Hassan Zali Boinee
Synthesis of β-Benzylsulfanyl-β-trifluoromethyl-α-amino
Acids Via Michael Addition in the Presence of Et3N/LiBr Pp.156-159
Dieter
Enders and Zai-Xin Chen
Chemistry for DOTA Peptide Labeling at Phenylalanine
Residues: On the Road to Preparing Peptide Ligand Tagged Libraries Pp.160-164
Luis
M. De Leon-Rodríguez, Zoltan Kovacs, and Alan D. Sherry
Synthesis of Pyranoid Sugar α-Amino Acid Derivatives
from 2-Oxo-Dgluconic Acid Pp.165-171
Stephan
Schmidt, Lars Teich, Mohamed Khodja and Dieter Sicker
Synthesis of Various Terphenyl Derivatives; Study of a
New Amine Receptor with a Terphenyl Structure Pp.172-175
Patricia
Le Nahenec-Martel, Stephane Leleu, Francis Marsais, Cyril Papamicael, Vincent
Levacher and Georges Dupas
Annulation of a 4-pyrrolylbutanal to a
5,6-dihydroindolizine Core: A Novel Diastereoselective Synthesis of
(±)-Indolizidine 167B Pp.176-178
Roberta
Settambolo, Giuditta Guazzelli and Raffaello Lazzaroni
Mild and Facile Deprotection for the Synthesis of
Oligodeoxynucleotide Incorporating a 6-O-Ethyl-deoxyguanosine Pp.179-183
Kohji
Seio, Tomoe Negishi, Kazuo Negishi and Mitsuo Sekine
Solution and Solid Phase Functionalization of
Imidazo[1,2-a]pyridines Pp.184-187
S.
El Kazzouli, A. Berthault, S. Berteina-Raboin, A. Mouaddib and G. Guillaumet
Chemical and Stereochemical Aspects of Oxidative
Coupling of Hphosphonate and H-Phosphonothioate Diesters. Reactions with N,N-,
N,O-and O,O-Binucleophiles Pp.188-197
Johan
Nilsson, Adam Kraszewski and Jacek Stawinski
A Mild and Efficient Synthesis of Disecondary
Phosphines Using CsOH: Efforts Toward Phosphine Macrocycles Pp.198-200
Matthew
T. Honaker and Ralph N. Salvatore
Abstracts
[Back to top] Recent Developments in Palladium-Catalyzed Coupling
Reactions
Pierre
van de Weghe
During the last few years major advances in Pd-catalyzed coupling reactions have been described; new catalyst systems based on bulky, electron-rich phosphines have been developed. This short report focuses on the recent progress in this area.
[Back to top] Stem Cells Differentiation: Organic Chemistry is Back
G.
Zanoni and A. Vadala
small organic molecules, able to induce, in vitro, osteogenesis, cardiomyogenesis, neurogenesis and dedifferentiation of stem cells, emerged form a library of heterocyclic compounds.
[Back to top] High-Yielding Synthesis of 3-Alkoxycarbonyl- and
3-Carboxamido-3-tropene Derivatives in Homogeneous Carbonylation Reactions of
3-Iodo-2-tropene
Laszlo
Horvath, Zoltan Berente and Laszlo Kollar
3-Iodo-2-tropene, synthesized from the corresponding ketone (tropinone) via its hydrazone, was carbonylated in palladium-catalyzed alkoxy- and aminocarbonylation reactions. The new synthetic approach provided the corresponding 3-carboxylic acid derivatives of pharmacological importance in chemospecific reactions and isolated in up to 87 % yields.
[Back to top] Highly Diastereoselective Epoxidation of a,b-Unsaturated Carbonyl Compounds Using
Sodium Peroxide
Valluru
Krishna Reddy, Buchammagari Haritha and Mitsuji Yamashita
A novel epoxidation method is described using sodium peroxide as an oxidant. A wide variety of α,β-unsaturated carbonyl compounds, particularly (E)-chalcones were oxidized to the corresponding epoxides in good to excellent yields. On the other hand, all reactions underwent smoothly in short reaction times, and the high reactivity of sodium peroxide was noticed for the first time toward the epoxidation of α,β-unsaturated carbonyl compounds, and kinetically proved. In all the cases, the epoxidation proceeded diastereospecifically.
[Back to top] Stereoselectivity in the Paterno-Buchi Reaction on Chiral
Allylic Alcohols, for A Discussion of the Hydroxy Directing Effect
Maurizio
D’Auria, Lucia Emanuele and Rocco Racioppi
The stereoselectivity of the photochemical reaction between acetophenone and 2,2,5-trimethyl-4-hexen-3-ol was explained on the basis of a DFT study. Conformational analysis of the starting material showed that two conformations were the most stable ones. Assuming that the attack of the excited carbonyl group occurred on the same side of the hydroxy group (due to hydrogen bond or to the formation of a complex), the possible conformations of the biradical intermediate was examined. Only the precursors of the threo stereoisomer was obtained in agreement with experimental results.
[Back to top] A Very Short and Efficient Synthesis of Preclamol
Arnault
de Filippis, Domingo Gomez Pardo and Janine Cossy
A very short and efficient synthesis of preclamol is described. The key step is the palladiumcatalysed arylation of the zinc enolate of N-propyl-2-piperidinone.
[Back to top] Brown Selectivity Disobedience of Hyperdeaminative
Friedel-Crafts Benzylation: Electrophilic Aromatic Substitutions via
Hyperdeaminatively Generated Benzyl Carbocations
R.W.
Darbeau, L.M. Siso, G.A. Trahan and R.S. Nolan
Hyperdeamination generates multiple spacer-molecule separated ion-pairs containing high-energy, relatively long-lived carbocations showing near specificity for arenes over their nascent counterions. They exhibit low intermolecular selectivity but surprisingly high intramolecular selectivity. Unlike analogous deaminative benzylations, hyperdeaminative benzylations disobey the Brown Selectivity Relationship. A model for EAS reactions with hyperactive electrophiles is proposed.
[Back to top] Lanthanide-Catalysed Cross-Cannizzaro Reduction of
Aromatic Aldehydes with Formaldehyde
Xiaogen
Yang, Jianping Guo and Gang Zou
Cross-Cannizzaro reaction catalysed by active Ln(OH)3 formed in situ was developed for practical reduction of aromatic aldehydes to the corresponding alcohols under a weakly basic aqueous condition. Improved functional group tolerance and selectivity were achieved using Et3N or DBU over dilute sodium hydroxide solution.
[Back to top] Influence of Homoallylic Fluorine Atoms on the
Regioselectivity of the Wacker Reaction
J.
Guidotti, M. Tordeux, J.-C. Blazejewski and C. Wakselman
Wacker oxidation reaction of terminal olefins bearing one or two fluorine atoms at a homoallylic position led to a ratio aldehyde/methyl ketone much higher than that observed with their non-fluorinated analogues. This regioselectivity can be ascribed to a specific interaction between fluorine atoms and palladium, or to a peculiar influence of the halogens on the double bond.
[Back to top] Rapid and Selective Acetalization of Aldehydes Using
Anhydrous Copper Sulfate Supported on Silica Gel (CuSO4 / SiO2)
Under Microwave Irradiation in Solvent-Free Conditions
Firouz
Matloubi Moghaddam, Afsaneh Arefi Oskoui and Hassan Zali Boinee
CuSO4 / SiO2 is found to be an efficient and selective medium for the acetalization of aldehydes in the presence of ketones in solvent-free conditions under microwave irradiation.
[Back to top] Synthesis of β-Benzylsulfanyl-β-trifluoromethyl-α-amino
Acids Via Michael Addition in the Presence of Et3N/LiBr
Dieter
Enders and Zai-Xin Chen
β-Benzylsulfanyl-β-trifluoromethyl-α-amino acid esters have been synthesized from (Z)-β-substituted-β-trifluoromethyl-α,β-dehydroamino acid esters via Michael addition with moderate diastereoselectivities. The reaction was investigated with various catalysts. Et3N and LiBr gave satisfactory results, which operated synergistically as bifunctional catalyst. However, the other tested chiral catalysts gave no good enantioselectivities.
[Back to top] Chemistry for DOTA Peptide Labeling at Phenylalanine
Residues: On the Road to Preparing Peptide Ligand Tagged Libraries
Luis
M. De Leon-Rodríguez, Zoltan Kovacs, and Alan D. Sherry
Different synthetic strategies to control the position of DOTA in phenylalanine residues within a peptide sequence were studied and compared. The results showed that use of DOTA pre-labeled amino acids stands as the most promising procedure for the synthesis of peptide ligand tagged libraries by solid phase peptide synthesis.
[Back to top] Synthesis of Pyranoid Sugar a-Amino Acid Derivatives from 2-Oxo-Dgluconic
Acid
Stephan
Schmidt, Lars Teich, Mohamed Khodja and Dieter Sicker
Syntheses of novel sugar amino acid derivatives with the 2-amino-D-arabino-hex-2-ulopyranosonic acid skeleton are described, with the anomeric centre being the a-C-atom of the amino acid unit. The starting material for the syntheses reported is 2-oxo-D-gluconic acid which has been obtained by fermentation of D-glucose. Starting from this source differently protected pyranoid a-sugar amino acids as well as derivatives like dipeptides could be synthesized.
[Back to top] Synthesis of Various Terphenyl Derivatives; Study of a
New Amine Receptor with a Terphenyl Structure
Patricia
Le Nahenec-Martel, Stephane Leleu, Francis Marsais, Cyril Papamicael, Vincent
Levacher and Georges Dupas
The synthesis of functionalized terphenyl derivatives was achieved starting from readily available 1,3-dichloro-2-iodobenzene. Among the prepared compounds, a molecule able to bind with benzylamine is described. This new host consist in a terphenyl structure possessing two side arms with aminomethylpyridines moieties. An interesting association constant with benzylamine and an unexpected 2/1 (host/guest) complex have been determined by using 1H NMR dilution experiments.
[Back to top] Annulation of a 4-pyrrolylbutanal to a
5,6-dihydroindolizine Core: A Novel Diastereoselective Synthesis of (±)-Indolizidine
167B
Roberta
Settambolo, Giuditta Guazzelli and Raffaello Lazzaroni
The synthesis of (±)-Indolizidine167B has been accomplished in 4 steps and 13.5 % overall yield from 4-carboxyethyl-4-(pyrrol-1-yl)butanal (1) via successive manipulations of 5,6-dihydroindolizine intermediates and final diastereoselective hydrogenation .
[Back to top] Mild and Facile Deprotection for the Synthesis of
Oligodeoxynucleotide Incorporating a 6-O-Ethyl-deoxyguanosine
Kohji
Seio, Tomoe Negishi, Kazuo Negishi and Mitsuo Sekine
The phenoxyacetyl (Pac) group proved to be useful for the synthesis of oligodeoxyribonucleotides incorporating a 6-O-ethylguanine. Since the Pac group could be removed by mild treatment with ammonia, formation of a 2, 4-diaminopurine derivative was avoided. Moreover, the use of the Pac group resulted in significant suppression of the depurination of 6-O-ethyldeoxyguanosine.
[Back to top] Solution and Solid Phase Functionalization of
Imidazo[1,2-a]pyridines
The Sonogashira cross-coupling with terminal alkynes and Buchwald coupling with aliphatic alcohols in position 6 of 2-phenylimidazo[1,2-a]pyridines was described. The position 3 was functionalized with various terminal alkynes in solution and on solid support to synthesize 3-substituted imidazo[1,2- a]pyridine derivatives.
[Back to top] Chemical and Stereochemical Aspects of Oxidative Coupling
of Hphosphonate and H-Phosphonothioate Diesters. Reactions with N,N-, N,O-and
O,O-Binucleophiles
Efficient protocols for oxidative coupling of dinucleoside H-phosphonate and dinucleoside Hphosphonothioate diesters with 6-aminohexan-1-ol, hexane-1,6-diamine, and hexane-1,6-diol, promoted by iodine were developed. In the instance of coupling with O-nucleophiles, the presence of t-butyldiphenylsilyl chloride and excess of iodine during oxidative coupling were found to have beneficial effect for these reactions in terms of rates and purity of the formed products.
[Back to top] A Mild and Efficient Synthesis of Disecondary Phosphines
Using CsOH: Efforts Toward Phosphine Macrocycles
Matthew T. Honaker and Ralph N. Salvatore
A mild and improved synthesis of disecondary phosphines PhPH(CH2)nPHPh (where n = 1-6), have been prepared. In the presence of phenylphosphine, cesium hydroxide, activated 4 Å molecular sieves and DMF, numerous dialkyl halides reacted efficiently to produce various disecondary phosphines exclusively at room temperature.