Paradigms and Paradoxes: The Position of the Lone Pair in Amines: A Comparison Between Bader’s AIM Approach and Pure Geometrical Considerations

The position of the lone pair of 17 amines has been located with the help of Baders AIM methodology. This position has been compared with those estimated with simple geometrical models. It appears that these models are convenient only for some symmetrical or undistorted cases.     

Investigations of the Chemistry of Alkyl Phosphites Toward Nitrogen-Containing Compounds: Efficient Approaches to α-Amino-, β-Amino-, and/or Enaminophosphonates

Abstract

In this study, we report recent investigations of the chemical reactivity of alkyl phosphites, mainly trialkyl and dialkyl phosphites, with molecules containing different nitrogen-containing compounds reported by us and other research groups over the past 25 years. Previous ground-breaking important reports are also considered. The reviewed investigations in this article are grouped according to only the type of the nitrogen-functional groups [amines (primary, secondary, and tertiary amines), imines, amides, thioamides, nitriles, isocyanates, isothiocyanates, oximes, hydrazones, diazo, and azides] and not according to the site of attack or the final products. Furthermore, the present review article focuses on the synthesis of α-amino-, β-amino-, and/or enaminophosphonates. These compounds have important roles in pharmaceutical chemistry.     

A New Approach to the Synthesis of Diethyl 2,3-Diisobutylsuccinate,a Component of Titanium–Magnesium Catalysts for Propylene Polymerization

Russian Journal of Applied Chemistry - A procedure was developed for preparing 2,3-dialkyl-substituted succinates by condensation of a succinic acid diester with two isobutyraldehyde molecules,...     

A New Heterocycle from the Reaction of N,N′-Dimethylthiourea with Diamino Phosphinoalkines

Abstract

The reaction of N,N′-dimethylthiourea with bis(dialkylamino)phosphinoalkines proceeds in two steps: 1) a transamination reaction, 2) ring closure by the nucleophilic attack of the sulfur atom at the C°C triple bond.     

Nitrimines: VII. Reaction of S,S′-Dimethyl-N-nitroimidodithiocarbonate with Alkali. Synthesis of S-Methyl-N-nitrothiocarbamate and Its Salts

Russian Journal of Organic Chemistry - Reaction of S,S′-dimethyl-N-nitroimidodithiocarbonate with alkali in aqueous-alcoholic solution results in salts of S-methyl-N-nitrothiocarbamate. In...     

A New Approach to 2,3-Dihydro-1H-1,5-Benzodiazepines from the Reaction of o-Nitrophenylazide with α,β-Unsaturated Ketones Promoted by Samarium Diiodide

Applications of samarium diiodide as a mild, neutral, selective and versatile single-electron transfer reducing and coupling reagent in organic synthesis have grown significantly in the last decade1. It is well known that both nitro compounds2a and azide compounds2b can be easily reduced by SmI2 to the corresponding amines. Little attention has been given to the intermediates derived from nitro or azide groups by treatment of SmI2, which may lead to reactions difficult to accomplish by other …     

Preparation of aminated taxol side chain precursors. A Simple Approach to 2,3-Diamond Acids Using the β-Lactam Synthon Method.

Coupling-ready aminated side chain analog precursors of the anticancer drug taxol were prepared through the β-lactam synthon method. The procedure described represents an easy connection between β-lactams and 2,3-diamino acids, is highly stereospecific, and causes no racemization due to vicinal group participation.     

New Approach to Analysis of the Nonlinearity of the Brønsted Relationship: II. An Empirical Procedure Combining the σρ Correlation Method with the Concept of Hard and Soft Acids and Bases,as Applied to Pseudo CH Acids

A comparative systematic analysis of the features of Brönsted behavior of pseudo CH acids(according to Eigen's classification) is made. The analysis is based on combined use of experimental data onpK _a, Ggas, logk _D of CH acids (Ggas is the free energy of acid ionization in the gas phase, logk _D isthe logarithm of the rate constant of hydrogen exchange in a protic solvent). The modified nucleophilicKabachnik constants ^- are applicable to correlations for all the three kinds of acidity of pseudo CH acids. The electrostatic solvation makes an insignificant contribution to variation of pK _a and weakening of the substituent effect in going from the gas phase to dimethyl sulfoxide, and also to differentiation of the kinetic acidity. The coefficient in the Brönsted equation and the ratio between the rate constants in the correlations, which characterize the degree of proton transfer in the reaction transition state, have much in common from the physical viewpoint. The results of correlation analysis, demonstrating intramolecular uniformity of the interactions, are fully consistent with the conclusion made in the previous part of this work about the solvation uniformity of the interactions, resulting in the absence of thermodynamic deviations from the Brönsted relationship.     

Reaction of β-Cyclodextrin with N-2,3-Epoxypropylphthalimide. Preparation, Characterisation and Study of a New Substituted Cycloheptaamylose. Effects on the Water Solubility of Drugs

The reaction of -cyclodextrinwith N-2,3-epoxypropylphthalimide yielded a set of newamorphous host compounds with high solubility whichwas transmitted to the corresponding host-guestcomplexes. The structure was determined by comparing the 1H- and 13C-NMR spectra with those of theparent compound, the degree of substitution by integration of the corresponding NMR signals, and C, H,and N elemental analysis.     

Cohalogenation of Alkenes: A New Base Induced Fragmentation Reaction of β, δ'-Dihalogenated Ethers to Oxiran and Butadiene. Indirect Oxygen Atom Transfer from THF

A new base induced fragmentation reaction of β, δ'-dihalogenated ethers leading to oxiran and butadiene is described.     

A Simple and Efficient New Approach to the Total Synthesis of (±)-4-Amino-3-(4-Chlorophenyl)-Butyric Acid (BACLOFEN)

Based on the utilization of a [2+2] cycloaddition reaction between dichloroketene and an appropriated olefin as a key step, we describe a new and simple four step approach to the total synthesis of (±)-4-amino-3-(4-chlorophenyl)-butyric acid (BACLOFEN), a selective GABA_B agonist used as antispastic agent     

A New Approach to the Construction of Pyrrolizidine and Indolizidine Skeleton: Enantioselective Synthesis of (1S, 7aS)-1-hydroxypyrrolizidine and (1S, 8aS)-1-hydroxyindolizidine

Pyrrolizidineandindolizidineareconunonstructura1elementsofmanynaturallyoccurringalkaloidsfoundinplantsandmicroorganisms.Thediverseandpotentbiologicalactivitiesofthesealkaloidshavedrawnmuchattentioninthestudiesoftheirpharmacologyandpreparation'.Ingeneral,mostconventionalsyntheticmethodologiesinvolvedthefinalformationofoneortwoC-Nbondsofpyrrolizidineandindolizidineskeleton'.andtheseresultedintheinefficientprotectinggroupchemistry,especiallywithrespecttohandlingtheaminoresidueTherefore.themostef…     

Relative Stabilities and Molecular Structures of the Geometrical Isomers of α,α′-Dioxasubstituted Cycloalkylidenecycloalkanes. A DFT Study

The relative stabilities and molecular structures of the geometrical isomers of seven ,-dioxa derivatives of cycloalkylidenecycloalkanes with 3to 6-membered rings have been studied by DFT calculations at the B3LYP/6-31G* level of theory. In each case, the E form was calculated to have the lower total energy. The relative energy of the Z isomer proved to increase regularly with increasing sizes of the two heterocyclic rings, ranging from 1.1 to 13.8 kJ mol^–1 on going from the 3,3to the 6,6-membered rings. Intermediate values of the relative energy were calculated for the Z forms of compounds containing two dissimilar rings. The relative energy of the Z isomer was found to be proportional to d ^–9.3, where d = the distance separating the two O atoms of the Z compound. The molecular structures, electric dipole moments, and atomic charges on the O atoms are also discussed.     

A novel reaction of β,β′-dihydroxy acids or esters with vanadium(V) trichloride oxide. New entry to the stereoselective synthesis of α-fluoro-α,β-unsaturated acids and esters

β,β′-Dihydroxy carboxylic acids and esters, readily prepared from dibromofluoroacetate and aldehydes, underwent deoxygenation, followed by elimination of aldehyde by the action of vanadium(V) trichloride oxide at the reflux temperature of chlorobenzene for 1 h to afford the Z isomers of α-fluoro-α,β-unsaturated acids and esters, respectively, in fair to good yields. This reaction provides a new alternative entry to the stereoselective synthesis of such fluoro compounds.