1,3-Alkadienephosphonic Amidoesters and Their Cyclization with Electrophilic Reagents

Abstract

The preparation of the titled compounds have been reported. The five-membered heterocyclization reaction of these compounds in the reaction with phosphorus-containing pseudohalogenes have been discussed.     

Synthesis and Structural Characterization of Butadienylcalcium-based Heavy Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex

The structure elucidation of heavy Grignard reagents (RAeX, Ae=Ca, Sr, and Ba, X=halides) has been greatly strived after, mainly because of their inaccessibility and remarkable instability. The synthesis of a series of butadienylcalcium compounds is presented, including 1-calcio-4-lithio-1,3-butadiene, 1,4-dicalcio-1,3-butadiene, and a Ca₄[O] inverse crown ether complex, via the reaction between 1,4-dilithio-1,3-butadienes and calcium iodide in THF. Single-crystal X-ray analysis of these unprecedented heavy Grignard reagents revealed unique structural characteristics and bonding modes. Preliminary reaction chemistry was investigated. This study provides a novel class of alkenyl heavy Grignard reagents and a useful synthetic strategy for otherwise unavailable reactive organometallic compounds.     

One-pot synthesis of α-trifluoromethylstyrenes from aryl ketones and the Ruppert–Prakash reagent

A new synthesis of α-trifluoromethylstyrenes from aromatic ketones and (trifluoromethyl) trimethylsilane is described. The reaction involves nucleophilic trifluoromethylation and elimination of trimethylsilanol, which are performed within one reaction flask.     

Decarboxylative Fluorination of Arylcarboxylic Acids Promoted by ortho‐Hydroxy and Amino Groups

A novel decarboxylative fluorination process has been developed for the synthesis of ortho‐hydroxy/amino arylfluorides from salicylic acid analogs, in which the ortho‐hydroxy/amino group plays an important role in the transformation. In addition, various arylfluorides are obtained in good to excellent yields under mild conditions.     

Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl

Grignard reagents RMgCl and their so‐called turbo variant, the highly reactive RMgCl?LiCl, are of exceptional synthetic utility. Nevertheless, it is still not fully understood which species these compounds form in solution and, in particular, in which way LiCl exerts its reactivity‐enhancing effect. A combination of electrospray‐ionization mass spectrometry, electrical conductivity measurements, NMR spectroscopy (including diffusion‐ordered spectroscopy), and quantum chemical calculations is used to analyze solutions of RMgCl (R=Me, Et, Bu, Hex, Oct, Dec, iPr, tBu, Ph) in tetrahydrofuran and other ethereal solvents in the absence and presence of stoichiometric amounts of LiCl. In tetrahydrofuran, RMgCl forms mononuclear species, which are converted into trinuclear anions as a result of the concentration increase experienced during the electrospray process. These trinuclear anions are theoretically predicted to adopt open cubic geometries, which remarkably resemble structural motifs previously found in the solid state. The molecular constituents of RMgCl and RMgCl?LiCl are interrelated via Schlenk equilibria and fast intermolecular exchange processes. A small portion of the Grignard reagent also forms anionic ate complexes in solution. The abundance of these more electron‐rich and hence supposedly more nucleophilic ate complexes strongly increases upon the addition of LiCl, thus rationalizing its beneficial effect on the reactivity of Grignard reagents.     

Synthesis of Some New Triphenylphosphanylidenes,Alkylphosphonates, and Heterocycles of Pyrazole Derivatives and Their Antimicrobial Activity

Abstract

The reaction of 5(4H)-pyrazolone with phosphorus ylides afforded new triphenylphosphanylidene alkanone derivatives. Moreover, its benzylidene derivative reacted with Wittig–Horner reagents to give the corresponding dialkoxyphosphoryl, alkyl phosphonate, and heterocyclic products. Treatment of pyrazole-4-carbaldehyde with Wittig–Horner reagents and trialkyl phosphites gave the respective alkyl phosphonate adducts. Mechanisms accounting for the formation of the new products are discussed. The biological activity of some of the newly synthesized compounds was also examined.     

Specific Occurence of Selenium in Certain Enzymes and Amino Acid Transfer Ribonucleic Acids

Abstract

Some enzymes known to contain selenium are enumerated. In four of them which catalyze coupled oxidation-reduction reactions the selenium occurs exclusively in the form of selenocysteine residues. Their structure and function are described in detail. Two other bacterial enzymes which contain selenium in the form of a labile, readily dissociable component are also described.

Results on the isolation, identification and structure determination of selenium-containing amino acid transfer ribonucleic acids are presented. These seleno-t RNA's are shown to contain either 5-methyl-aminomethyl-2-selenouridine or other 2-selenouridine derivatives. The role of selenium in a glutamate iso-accepter species is discussed.     

HYDROBORATION OF UNSATURATED AMINES X. HYDROBORATION-HALOGENATION OF ALLYL PHOSPHORAMIDATES ROUTE TO γ-HALOGENOPROPYL PHOSPHORAMIDATES AND γ-HALOGENATED AMINES

Abstract

This paper describes the synthesis of γ-halogenopropyl phosphoramidates I by hydroboration-halogenation reaction of N-phosphorylated allylamines II (phosphoramidates and phosphoramides). Only the use of allyl phosphoramidates leads to a good regioselectivity of the addition of boron atom on the terminal carbon atom of the allyl structure (compounds III).

The absence of N→B complex formation permits a good reactivity of the trialkylboranes III and IV. The breaking of the P[sbnd]N bond, in acidic medium of the compounds I gives corresponding γ-halogenated amines V.     

Very Simple One-Step Synthesis of Vinylphosphonates and Enamine Phosphonates by Direct Addition of Organolithium Reagents to 1-Alkynylphosphonates

Abstract

Direct addition of organolithium to 1-alkynylphosphonates (1) afforded vinylphosphonates and enamine phosphonates (2) in good to excellent yields. The reaction was carried out in dry THF at low temperature and proved to be completely stereoselective (syn addition). Alkyl, aryl, and haloalkyl groups were attached to the alkynyl entity, so the resulting vinylphosphonates contained various functional groups. The stereochemistry of the products as well as mechanism of the reaction were determined based on ¹H and ¹³C NMR. The synthesis of enamine phosphonates in the absence of complicated, highly expensive organometallic catalysis has not been previously reported.