Ammonia Equivalent Research Articles

Sonogashira Coupling with Aqueous Ammonia.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Sonogashira Coupling with Aqueous Ammonia

Abstract The coupling reaction of terminal alkynes with organic halides, Sonogashira-(Hagihara) coupling, takes place with only 2 equivalents of dilute aqueous ammonia as an additive. The reaction of phenylacetylene and 4-iodoanisole in the presence of 1 mol% of PdCl2(PPh3)2, 2 mol% of CuI, and 2 equiv of aqueous ammonia in THF proceeds at room temperature for 6 h to afford the coupling product in a quantitative yield.

ChemInform Abstract: Palladium‐Catalyzed Synthesis of Arylamines from Aryl Halides and Lithium Bis(trimethylsilyl)amide as an Ammonia Equivalent.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New ammonia equivalents for the Pd-catalyzed amination of aryl halides.

[reaction: see text]. LiN(SiMe3)2, Ph3SiNH2, and LiNH2 can be be used as ammonia equivalents for the Pd-catalyzed coupling of aryl halides. Using these amine derivatives, simple anilines, including ortho-substituted ones, as well as di- and triarylamines can be readily prepared.

Palladium-catalyzed synthesis of arylamines from aryl halides and lithium bis(trimethylsilyl)amide as an ammonia equivalent.

[reaction: see text]. A simple, palladium-catalyzed method to convert aryl halides to the parent anilines using lithium bis(trimethylsilyl)amide (LiN(SiMe3)2) is reported. The reaction is catalyzed by Pd(dba)2 and P(t-Bu)3 and can be run with as little as 0.2 mol % of catalyst. The reaction is faster than competing generation of benzyne intermediates and, therefore, provides the aniline products regiospecifically.

An Ammonia Equivalent for the Dimethyltitanocene-Catalyzed Intermolecular Hydroamination of Alkynes.

Commercially available alpha-aminodiphenylmethane 1 (benzhydrylamine) serves as a convenient ammonia equivalent in the dimethyltitanocene-catalyzed intermolecular hydroamination of alkynes. The primary formed imines can be hydrogenated and cleaved directly to the corresponding primary amines by catalytic hydrogenation using Pd/C as catalyst.

Enantioselective synthesis of unsaturated amino acids using p-methoxybenzylamine as an ammonia equivalent

A versatile, non-alkylative enantioselective synthesis of unsaturated α-amino acids based on the Sharpless asymmetric epoxidation has been developed. Enantiomerically enriched trans epoxy alcohols bearing unsaturated substituents were prepared and submitted to regio- and stereospecific ring-opening with p-methoxybenzylamine as a nucleophile, leading to anti-3-( p-methoxybenzylamino)-1,2-diols which were further protected by reaction with Boc 2O. The 1,2-diol fragment was then oxidatively cleaved by a sequential treatment with sodium periodate and sodium chlorite to afford the corresponding amino acid. Using this methodology, doubly N-protected ( p-methoxybenzyl and Boc) allyl glycine, 3-butenyl glycine and 4-pentenyl glycine have been prepared in three synthetic steps from the corresponding allyl alcohols. As a demonstration of the orthogonal nature of the nitrogen protection, both protecting groups have been selectively removed from the fully protected amino ester.

Synthesis of azepane scaffolds on solid support for combinatorial chemistry

Enantiopure C 2-symmetric azepanes have been synthesized on solid support as scaffolds for the synthesis of peptidomimetics in combinatorial chemistry. The key step involves Rink resin as a formal equivalent of ammonia in the nucleophilic opening of L-iditol bis-epoxide.

Allyl amines as ammonia equivalents in the preparation of anilines and heteroarylamines

A series of anilines and heteroarylamines were synthesized in moderate to excellent yields by palladium catalyzed cross coupling reaction of aryl or heteroaryl halides with allyl- or N,N-diallylamine followed by deallylation.

ChemInform Abstract: An Ammonia Equivalent for the Palladium‐Catalyzed Amination of Aryl Halides and Triflates.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Diastereo‐ and Enantioselective Synthesis of β‐Amino Acids via SAMP Hydrazones and Hetero Michael Addition Using TMS‐SAMP as a Chiral Equivalent of Ammonia

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

An Ammonia Equivalent for the Palladium-Catalyzed Amination of Aryl Halides and Triflates

Commercially available benzophenone imine serves as a convenient ammonia equivalent in the palladium-catalyzed amination of aryl halides and triflates. The benzophenone imine adducts can be cleaved directly to the corresponding primary anilines by catalytic hydrogenation or treatment with hydroxylamine hydrochloride or a catalytic amount of HCl in wet THF. © 1997 Elsevier Science Ltd.

Determinants of Ammonia Clearance by Hemodialysis

Ammonia toxicity appears to contribute to the genesis of brain edema, a leading cause of death in fulminant hepatic failure. Because dialysis has been recommended for acute hyperammonemia in other conditions, we have conducted a study to analyze the determinants of ammonia clearance with the use of a single-pass dialyzer. We have used an ionic solution with a constant concentration of ammonia to estimate clearance at different blood flow rates, at dialysate flow rates, and with different dialyzer surfaces. Once hemodialysis had been optimized, we estimated ammonia, glutamine, and urea removal by using a single-compartment model. Our results show that the clearance of ammonia is blood flow dependent and is also influenced by dialysate flow rate and dialyzer surface. At clinically feasible conditions, ammonia can be extracted by more than 80% by setting the dialysate flow at a high rate. In addition to ammonia removal, hemodialysis allows the clearance of urea and glutamine, molecules that can be regarded as ammonia equivalents and that also undergo flow-dependent elimination.

The Use of Vicinal Twofold Heck Reaction Products in Diastereoselective Sequential Michael Additions — A Convenient Access to Enantiomerically Pure Six‐Ring Anellated Cispentacin Derivatives

AbstractThe palladium‐catalyzed coupling reactions of various acrylic acid derivatives 2a–e (e.g. methyl, tert‐butyl, benzyl, menthyl esters) with 1,2‐dibromobenzene (1), 1,2,3‐tribromobenzene (4) and 1,2‐dibromocyclohexene (6) yielded the correspondingly substituted ortho‐diethenylarenes 3a–e, 1,2,3‐triethenylarenes 5a,b and (E,E)‐1,3,5‐hexatriene derivatives 7a,b. Some of these vicinal diacrylates (3a–d, 5b, 7a,b) were converted to 1,2,3‐trisubstituted indane‐ and tetrahydroindane derivatives 10a–d, 15a,b, 18, 20, 23, and 12a,b, 16b by domino conjugate addition of nitrogen, carbon, and sulfur nucleophiles. With benzyl(trimethylsilyl)amine (9) as an ammonia equivalent, the relative configuration of all three newly formed stereogenic centers was controlled (d.e. >90%). Therefore, with chiral non‐racemic ammonia equivalents like benzyl[(S)‐phenylethyl]amine (14) and TMS‐(R)‐AMP (17), protected diastereomerically pure β‐amino esters were obtained, which could easily be deprotected by standard methods to yield the enantiomerically pure β‐amino acids 27 and 28.

Stereoselective synthesis of?-amino acids via conjugate addition of nitrogen nucleophiles to?,?-unsaturated esters ? Recent advances

The latest results concerning the asymmetric synthesis ofβ-amino acids are reviewed, focussing on methodology involving 1,4-addition of nitrogen nucleophiles toα,β-unsaturated esters. Approaches using both homochiral auxiliaries bound to the enoate and homochiral ammonia equivalents are included as well as alkylations and aldol reactions of enolates derived from homochiralβ-amino acids.

ChemInform Abstract: Diastereo‐ and Enantioselective Synthesis of trans‐2‐Amino‐cycloalkane‐ 1‐carboxylic Acids via Intramolecular Tandem Michael Addition/α‐ Alkylation Using TMS‐SAMP as Chiral Equivalent of Ammonia.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Lithium (α‐Methylbenzyl)allylamide: A Differentially Protected Chiral Ammonia Equivalent for the Asymmetric Synthesis of β‐Amino Acids and β‐Lactams.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Enantioselective Synthesis of β‐Amino Acids: TMS‐SAMP as a Chiral Ammonia Equivalent for the Aza Analogous Michael Addition to α,. beta.‐Unsaturated Esters.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Diastereo‐ and Enantioselective Synthesis of α‐Substituted β ‐Amino Acid Esters by Tandem Michael‐Addition/α‐Alkylation with TMS‐SAMP as Chiral Equivalent of Ammonia.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Diastereo- and Enantioselective Synthesis of trans-2-Amino-Cycloalkane-1-Carboxylic Acids via Intramolecular Tandem Michael-Addition/α-Alkylation Using TMS-SAMP as Chiral Equivalent of Ammonia

Diastereo- and Enantioselective Synthesis of trans-2-Amino-Cycloalkane-1-Carboxylic Acids via Intramolecular Tandem Michael-Addition/α-Alkylation Using TMS-SAMP as Chiral Equivalent of Ammonia