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M Beller

Publications and source records attributed to M Beller.

At least 19 recordsLinked to original sources
PubMed2001

A convenient rhodium-catalyzed intermolecular hydroamination procedure for terminal alkynes.

The first rhodium-catalyzed intermolecular hydroamination of alkynes is presented. Terminal alkynes react efficiently with anilines in the presence of cationic rhodium(I) catalysts under very mild reaction conditions (e.g., base and acid free at room temperature) to yield up to 99% of the corresponding imines. An easy one-pot protocol for the synthesis of secondary amines was developed by combining this alkyne amination reaction with in situ addition of organolithium reagents.

Journal Article↗
PubMed2001

Facile three-component coupling procedure for the synthesis of substituted tetrahydroisoindole-1,3-diones from alpha,beta-unsaturated aldehydes.

[reaction: see text]. A new one-pot procedure for the efficient synthesis of a small library of amino-functionalized tetrahydroisoindole-1,3-dione derivatives was developed. This three-component coupling reaction comprises subsequent condensation and Diels-Alder reactions of ubiquitous available starting materials (alpha,beta-unsaturated aldehydes, amide, and maleimide). The synthesized compounds share a substituted tetrahydroisoindole motif in an endo fashion.

Journal Article↗
PubMed2001

Palladium catalyst systems for cross-coupling reactions of aryl chlorides and olefins.

A detailed investigation into the influence of phosphines, additives, bases and solvents on the Heck coupling reaction of 4-trifluoromethyl-1-chlorobenzene (2) is presented. It is shown that a number of catalyst systems exist for efficient cross coupling of electron-deficient aryl chlorides with various olefins. Basicity and steric demand of the ligand are two factors which determine the success of the reaction. In addition the phosphine/palladium ratio, the correct type and amount of additive, and finally the use of an appropriate base and solvent are also important. The optimised reaction conditions are applied for the arylation of styrene, 2-ethylhexyl acrylate and N,N-dimethyl acrylic amide with various aryl chlorides.

Journal Article↗
PubMed2001

Synthesis of primary aromatic amides by aminocarbonylation of aryl halides using formamide as an ammonia synthon.

Primary aromatic amides were prepared by a palladium-catalyzed aminocarbonylation reaction of aryl halides in high yields (70-90%) using formamide as the amine source. The reactions require a palladium catalyst in combination with a nucleophilic Lewis base such as imidazole or 4-(dimethylamino)pyridine (DMAP). Aryl, heteroaryl, and vinyl bromides and chlorides were converted to the primary amides under mild conditions (5 bar, 120 degrees C) using 1 mol % of a palladium-phosphine complex. Best results were obtained in dioxane using triphenylphosphine as the ligand and DMAP as the base. For activated aryl bromides, a phosphine-to-palladium ratio of 2:1 was sufficient, but less reactive aryl bromides or aryl chlorides required ligand-to-palladium ratios up to 8:1 in order to stabilize the catalyst and achieve full conversion. The influence of catalyst, base, solvent, pressure, and temperature was studied in detail. The mechanism of the reaction could be clarified by isolating and identifying the reaction intermediates. In addition, methylamides and dimethylamides were prepared by the same method using N-methylformamide and N,N-dimethylformamide as the amine source.

Journal Article↗
PubMed2001

Synthesis of 2,3-dihydroindoles, indoles, and anilines by transition metal-free amination of aryl chlorides.

Aliphatic and aromatic amines react with 2- and 3-chlorostyrene in the presence of potassium tert-butoxide to give N-substituted 2,3-dihydroindoles in good yields. The combination of this domino-amination protocol with a suitable dehydrogenation reaction gives access to pharmacologically interesting indoles in a one-pot procedure. Overall product yields of N-substituted indoles >50% are obtained by this method starting from commercially available substrates. In addition to the intramolecular base-promoted amination of aromatic C-Cl bonds, metal-free intermolecular aminations of aryl chlorides with primary and secondary amines are described. The use of potassium tert-butoxide as base allows the synthesis of various anilines in good to excellent yields. Due to the formation of aryne intermediates, either N-substituted anilines or meta-substituted anilines are produced with excellent selectivities.

Journal Article↗
PubMed2001

Base-catalyzed amination of olefins: an example of an environmentally friendly synthesis of amines.

The base-catalyzed amination of aromatic olefins is described as an environmentally friendly synthesis of various beta-arylethylamines. Primary and secondary aliphatic amines as well as aromatic amines react with styrene derivatives to give the corresponding beta-arylethylamines in high yield up to 99%. While aliphatic amines react with styrenes in the presence of n-BuLi as the pre-catalyst, anilines can be olefinated using KOtBu as the catalyst.

Alkenes↗
PubMed2001

The effect of imaging modality on patient management in the evaluation of pulmonary thromboembolism.

A retrospective medical record review was performed to study the differences in clinical risk profiles and the relationships between test results versus management for suspected pulmonary thromboembolism (TE) in patients undergoing either radionuclide ventilation perfusion (V/Q) scans or pulmonary computed tomographic angiography (CTA), as the initial test. Data of 138 consecutive V/Q patients were compared with that of 149 consecutive CTA patients during equivalent 6-month intervals before and after the introduction of CTA. Information on risk factors, signs and symptoms, all diagnostic test results, and the relationships between the test results and ultimate physician management were collected and analyzed. V/Q results predicted physician management in all patients with high probability scans and 91% with normal to low probability scans. There were 35 patients with indeterminate V/Q scans--43% of these patients were managed without any other diagnostic test. CTA results predicted management in all patients with positive studies and 99% of patients with negative studies. In contrast to the V/Q cohort, only seven CTA studies were inconclusive--additional diagnostic tests determined management in all but one case. Compared with V/Q, CTA has fewer indeterminate results, is more directly reflective of management, and reduces the number of patients managed with inconclusive data.

Algorithms↗
PubMed2000

A New Highly Efficient Catalyst System for the Coupling of Nonactivated and Deactivated Aryl Chlorides with Arylboronic Acids Palladium-Catalyzed Reactions for Fine Chemical Synthesis, Part 17. The authors thank C. Fuhrmann for the excellent support in the laboratory, Dipl.-Chem. W. Mägerlein for ligand samples of 2-(dicyclohexylphosphanyl)toluene and -anisole as well as DMC(2) for generous donations of palladium compounds. Part 16: F. Vollmüller, W. Mägerlein, S. Klein, J. Krause, M. Beller, Adv. Synth. Catal., in press.

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Journal Article↗
PubMed2000

Amination of aromatic olefins with anilines: a new domino synthesis of quinolines.

A new catalytic amination of aromatic olefins with anilines is presented. In a domino reaction, substituted quinoline derivatives are obtained in the presence of cationic rhodium complexes, such as [Rh(cod)2]BF4, and PPh3. Ethylbenzene is formed as a by-product in this new oxidative reaction. The first transition metal catalyzed anti-Markovnikov hydroamination of styrene with anilines occurs as a side reaction. Mechanistic investigations strongly support the regioselective oxidative amination of styrene as the key reaction step.

Alkenes↗
PubMed2000

Palladium/phosphite catalyst systems for efficient cross coupling of aryl bromides and chlorides with phenylboronic acid

The Suzuki reaction of aryl bromides is efficiently catalyzed by palladium/ phosphite complexes generated in situ. The influence of ligand, base, and different additives is examined. The process tolerates various functional groups and catalyst turnover numbers up to 820,000 are obtained even with deactivated aryl bromides. For the first time it is shown that palladium/phosphite complexes also catalyze efficiently the Suzuki reaction of aryl chlorides.

Journal Article↗
PubMed2000

Amidocarbonylation-An Efficient Route to Amino Acid Derivatives.

Atom efficient, multicomponent reactions that lead to high-value products from inexpensive starting materials are of both economic and ecological interest for industrial organic synthesis. alpha-Amino acids are amongst the most important compounds in chemistry and biology. As well as their biochemical significance as building blocks of peptides and proteins, alpha-amino acids are also becoming increasingly interesting as fine chemicals. Possibly one of the key reactions in the preparation of these compounds is transition metal catalyzed amidocarbonylation, where the alpha-amino acid framework is constructed in a single step from an aldehyde, an amide, and carbon monoxide. This article gives a current overview of transition metal catalyzed amidocarbonylation reactions used in the synthesis of alpha-amino acids derivatives. A classification and summary of the significant features of this three component reaction is first presented together, with an historical introduction. This section is followed by two sections on cobalt- and palladium-catalyzed amidocarbonylation. A discussion of the mechanism of each of the different amidocarbonylation variants form an introduction. Overviews on further synthetic development of the methodology, such as the domino reaction with an amidocarbonylation step and the expansion of the range of starting materials, form the main topics of both variants. The potential of the method is demonstrated with the help of examples of special synthetic utility (for example, the preparation of arylglycines). Finally, possibilities for future developments in transition metal catalyzed amidocarbonylation reactions are proposed on the basis of the current state of knowledge.

Journal Article↗
PubMed1998

Measles outbreak in Juneau, Alaska, 1996: implications for future outbreak control strategies.

OBJECTIVE: To determine the most effective outbreak control strategy for school-based measles outbreaks as the proportion of children with two doses of measles-containing vaccine (MCV) increases. SETTING: A school-based measles outbreak during 1996 involving 63 cases in Juneau, Alaska (population 29 288), where systematic revaccination with MCV was not implemented. DESIGN: A retrospective evaluation using chain-of-transmission data of three possible outbreak control strategies: no school revaccination, targeted school revaccination (affected schools only), and community-wide school revaccination (all schools). Two-dose MCV coverage among students was estimated from school vaccination records and a survey issued to parents. PRIMARY OUTCOME MEASURES: Potentially preventable cases of measles and doses of MCV administered per case prevented. RESULTS: Two-dose MCV coverage among Juneau students was estimated to be 44% and 53% immediately before and after the outbreak, respectively. Of all the measles cases, an estimated 24 to 28 and 27 to 31 were potentially preventable by the targeted and community-wide school revaccination strategies, respectively. Either strategy might have optimally decreased the outbreak duration by 1 month, sparing one of seven affected schools and 10 of 12 unvaccinated children who had measles. Approximately 133 to 155 and 139 to 160 doses of MCV per case prevented would have been required for targeted and community-wide school revaccination, respectively. CONCLUSIONS: Either targeted or community-wide school revaccination would have been effective control strategies for this outbreak. Targeted school revaccination is probably the intervention of choice for school-based measles outbreaks in larger communities with higher two-dose MCV coverage. As two-dose MCV coverage continues to increase in the United States, public health control measures to respond to outbreaks need to be reevaluated.

Adolescent↗
PubMed1997

Alcohol-related injury death and alcohol availability in remote Alaska.

CONTEXT: Injury is a major public health problem in Alaska, and alcohol consumption and injury death are associated. OBJECTIVE: To determine the association between injury death, particularly alcohol-related injury death, and alcohol availability in remote Alaska. DESIGN, SETTING, AND PARTICIPANTS: Survey using death certificate data and medical examiner records to compare mortality rates for total injury and alcohol-related injury during 1990 through 1993 among Alaskans aged 15 years and older who had resided in remote villages of fewer than 1000 persons. MAIN OUTCOME MEASURES: Rate ratios of injury death among residents of wet villages (ie, those without a restrictive alcohol law) as compared with injury death among residents of dry villages (ie, those with laws that prohibited the sale and importation of alcohol). RESULTS: Of 302 injury deaths, blood alcohol concentrations (BACs) were available for 200 deaths (66.2%). Of these, 130 (65.0%) had a BAC greater than or equal to 17 mmol/L (> or =80 mg/dL) and were, therefore, classified as alcohol related. The total injury mortality rate was greater among Alaska Natives from wet villages (rate ratio [RR],1.6; 95% confidence interval [CI], 1.3-2.1), whereas this difference was not present for nonnatives (RR, 1.1; 95% CI, 0.3-3.8). For Alaska Natives, the alcohol-related injury mortality rate was greater among residents of wet villages (RR, 2.7; 95% CI, 1.9-3.8) than among residents of dry villages. The strength of this association was greatest for deaths due to motor vehicle injury, homicide, and hypothermia. CONCLUSIONS: Although insufficient data existed to adjust for the effects of all potential confounders, residence in a wet village was associated with alcohol-related injury death among Alaska Native residents of remote Alaska villages. These findings indicate that measures limiting access to alcoholic beverages in this region may decrease alcohol-related injury deaths.

Accidents↗