Kinetics studies of 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol,and 2,4,4-trimethyl-1-pentanol with chlorine atoms: Photooxidation mechanism of 2,4,4-trimethyl-1-pentanol

The rate constants for the reaction between chlorine atoms and either 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, or 2,4,4-trimethyl-1-pentanol at 298 K were determined using the relative method with 2-butanol and 1-pentanol as reference compounds. The values obtained for 5-methyl-2-hexanol, 2,2-dimethyl-3-hexanol, and 2,4,4-trimethyl-1-pentanol (k × 10¹⁰ cm³ molec⁻¹ s⁻¹) were, respectively, (2.64 ± 0.5), (2.72 ± 0.5), and (2.50 ± 0.4), in agreement with the values of the rate constants reported in bibliography for similar alcohols and the values estimated by structure activity relationship methods. The photooxidation products of 2,4,4-trimethyl-1-pentanol initiated by chlorine atoms were identified (formaldehyde, 2-propanone, 2,2-dimethyl propanal, 4,4,-dimethyl-2-pentanone, and 3,3-dimethylbutanal), and the reaction mechanism was determined.     

IR spectroscopic study of the reaction of dihydroxyorganocyclosiloxanes with 2,2-dimethyl-1-oxa-2-silacyclohexane

The reaction of various mono- and dihydroxyorganocyclosiloxanes with 2,2-dimethyl-1-oxa-2-silacyclohexane was studied by IR spectroscopy. A series of new bis[dimethyl(hydroxybutyl)siloxy] organocyclosiloxanes were obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1134–1137, June, 1995.     

5,5-dimethyl-1,3-dioxan-4-ol as orthogonally protected equivalent of 2,2-dimethyl-3-hydroxypropanal

Condensation of isobutyraldehyde with aqueous formaldehyde in the presence of Ba(OH)2 gave a new gem-dimethyl-substituted building block.     

Fragment-guided approach to incorporating structural information into a CoMFA study: BACE-1 as an example

Alzheimer’s disease is an ultimately fatal neurodegenerative disease, and BACE-1 has become an attractive validated target for its therapy, with more than a hundred crystal structures deposited in the PDB. In the present study, we present a new methodology that integrates ligand-based methods with structural information derived from the receptor. 128 BACE-1 inhibitors recently disclosed by GlaxoSmithKline R&D were selected specifically because the crystal structures of 9 of these compounds complexed to BACE-1, as well as five closely related analogs, have been made available. A new fragment-guided approach was designed to incorporate this wealth of structural information into a CoMFA study, and the methodology was systematically compared to other popular approaches, such as docking, for generating a molecular alignment. The influence of the partial charges calculation method was also analyzed. Several consistent and predictive models are reported, including one with r ² = 0.88, q ² = 0.69 and r _pred² = 0.72. The models obtained with the new methodology performed consistently better than those obtained by other methodologies, particularly in terms of external predictive power. The visual analyses of the contour maps in the context of the enzyme drew attention to a number of possible opportunities for the development of analogs with improved potency. These results suggest that 3D-QSAR studies may benefit from the additional structural information added by the presented methodology.     

Gold anode corrosion in an aqueous solution of 2,2-dimethyl-1,3-diaminopropane

Russian Chemical Bulletin - The kinetics and mechanism of corrosion of an Au anode in a weakly basic aqueous solution of 2,2-dimethyl-1,3-diaminopropane (2,2-DM-1,3-DAP) were studied by gravimetry...     

Stereoconservative Negishi arylation and alkynylation as an efficient approach to enantiopure 2,2'-diarylated 1,1'-binaphthyls

Negishi arylation and alkynylation of easily synthesized chiral 2,2'-diodo-1,1'-binaphthyl rapidly proceeds in refluxing THF utilizing controlled microwave irradiation, affording enantiopure 2,2'-diarylated 1,1'-binaphthyls in good to excellent yields.     

3-二氯乙酰基-2,5-二甲基-2-乙基-1,3-（噁）唑烷的一锅法合成与生物活性

利用“一锅法”合成了标题化合物 ,经元素分析 ,IR和1 H NMR确定了结构 ,并对产物进行了初步的生物活性测定。     

New selective haloform-type reaction yielding 3-hydroxy-2,2-difluoroacids: theoretical study of the mechanism

Experimental results of an unprecedented haloform-type reaction in which 4-alkyl-4-hydroxy-3,3-difluoromethyl trifluoromethyl ketones undergo base-promoted selective cleavage of the CO-CF(3) bond, yielding 3-hydroxy-2,2-difluoroacids and fluoroform, are rationalized using DFT (B3LYP) calculations. The gas-phase addition of hydroxide ion to 1,1,1,3,3-pentafluoro-4-hydroxypentan-2-one (R) is found to be a barrierless process, yielding a tetrahedral intermediate (INT), involving a DeltaG(r)(298 K) of -61.4 kcal/mol. The CO-CF(3) bond cleavage in INT leads to a hydrogen-bonded [CH(3)CHOHCF(2)CO(2)H...CF(3)](-) complex by passage through a transition structure (TS1) with a DeltaG()(298 K) of 20.8 kcal/mol and a DeltaG(r)(298 K) of 9.8 kcal/mol. This complex undergoes a proton transfer between its components, yielding a hydrogen-bonded [CH(3)CHOHCF(2)CO(2)...CHF(3)](-) complex. This process has associated with it a DeltaG()(298 K) of only 3.1 kcal/mol and a DeltaG(r)(298 K) of -43.3 kcal/mol. The CO-CF(2) bond cleavage in INT leads to a hydrogen-bonded [CH(3)CHOHCF(2)...CF(3)CO(2)H](-) complex by passage through a transition structure (TS3) with a DeltaG()(298 K) of 29.2 kcal/mol and a DeltaG(r)(298 K) of 25.1 kcal/mol. The lower energy barrier found for CO-CF(3) bond cleavage in INT is ascribed to the larger number of fluorine atoms stabilizing the negative charge accumulated on the CF(3) moiety of TS1, as compared to the number of fluorine atoms stabilizing the negative charge on the CH(3)CHOHCF(2) moiety of TS3. The solvent-induced effects on the two pathways, introduced within the SCRF formalism through PCM calculations, do not reverse the predicted preference of the CO-CF(3) over the CO-CF(2) bond cleavage of R in the gas phase.     

Indium-mediated Reformatsky reaction on lactones: preparation of 2-deoxy-2,2′-dimethyl-3-ulosonic acids

Indium-mediated Reformatsky reactions of simple lactones and aldonolactones with ethyl α-bromoisobutyrate allow the synthesis of the corresponding ketals and ulosonic acid esters, respectively, in good yields.     

Use of monoterpenes, 3-carene and 2-carene, as synthons in the stereoselective synthesis of 2,2-dimethyl-1,3-disubstituted cyclopropanes

The current review represents a systematic survey of the use of 2- and 3-carenes in the synthesis of chiral non-racemic organic compounds containing a 2,2-dimethyl-1,3-disubstituted cyclopropane fragment. The synthetic approaches to the cyclopropane derivatives are classified on the basis of the retention of their parent carane bicyclic skeleton in the final product or cleavage of the six-membered ring along the synthetic route.     

IR spectroscopic study of polymer blends and composites: A new approach

The particle size distributions of fillers in the films of polymer composites and blends have been investigated by IR spectroscopy and optical and electron microscopy. A new effective spectroscopic technique is proposed for determining the particle concentration, average size, and size distribution of the filler and the character of aggregation of these particles in the bulk of the polymer matrix. The proposed technique is based on the analysis of IR radiation intensity attenuation due to light scattering on filler particles in the polymer matrix. The spectroscopic data are in good agreement with the results of microscopic experiments.     

Lipase catalyzed acylation of primary alcohols with remotely located stereogenic centres: the resolution of (±)-4,4-dimethyl-3-phenyl-1-pentanol

Enantioselective acylation of some (±)-3-alkyl-3-phenyl-1-propanols was performed with enzymes as catalysts. Moderate enantiomeric ratios (E), ranging up to E = 11.6, were obtained. In the resolution, some of the lipases selectively acylated the (+)-enantiomer while others acylated the (−)-enantiomer of the γ-substituted primary alcohols 1–4. Thus, it is possible to obtain both enantiomers of the alcohols as remaining substrate with high enantiomeric purity. The resolution of (±)-4,4-dimethyl-3-phenyl-1-pentanol 4 was extensively studied and screening experiments were conducted to select suitable lipase(s), reaction medium, acyl donor and appropriate temperature combinations to increase the enantiomeric ratio. Chirazyme^® L-6/chloroform/vinyl propionate/38 °C and Chirazyme^® L-7/di-iso-propyl ether/vinyl propionate/0 °C were chosen to obtain both enantiomers, (R)-(+)-4 and (S)-(−)-4, respectively, via sequential resolutions in excellent enantiomeric excess (>98%) and in 25% and 22% yield, respectively.     

Topological studies related to molecular systems formed during the Big Bang: H3+ as an example

In the present article are analyzed the non-adiabatic coupling terms (NACT) for two molecular systems, namely H₃⁺ and H₃. In contrast to previous occasions in which the NACTs are studied along (closed) circular contours usually surrounding conical intersections (ci), in the present article are studied distribution of the NACTs in (planar) configuration spaces (CS). The motivation for this study has to do with a novel idea being mentioned earlier (Molec. Phys., 116, 2435 [2018]; ArXiv:1801.00103) that NACTs are like a Glue (eventually) associated with the ability of creating molecules and/or protecting them from breaking up. It was found that the distributions of the NACTs due to the two molecules are similar as long as the attention is given to regions close to their equilateral cis, but then they behave significantly different in other regions. In case of H₃⁺, the NACTs are distributed rather uniformly whereas, in case of H₃ they become spiky the closer they approach the diatom axis. The main conclusion of this study is that the glue which has its origin in the NACTs is most likely to be effective in case of H₃⁺ that explains the creation and later survival of this molecule.     

1H NMR study of self-association of actinomycin D in an aqueous solution

This paper presents the results of a proton magnetic resonance study (500 MHz) of self-association of actinomycin D (AMD) antibiotic in an aqueous solution. The equailibrium constants and thermo-dynamic parameters (ΔH, ΔS) of molecular association as well as the limiting values of proton chemical shifts of associate molecules were determined from the concentration and temperature dependences of¹H NMR chemical shifts of AMD. The results were analyzed using dimeric and infinite-dimensional cooperative models of molecular self-association. The value of the cooperativity parameter indicates that AMD self-association is anticooperative, i.e., formation of aggregates larger than dimers is energetically unfavorable. The values of induced proton chemical shifts were used to determine the most probable mutual orientation of chromophores in AMD structure. Sevastopol State Technical University. Berkbeck College, London University. Translated fromZhurnal Struktumoi Khimii, Vol. 36, No. 1, pp. 81–88, January–February, 1995. Translated by L. Smolina     

Quantitative analysis of the compounds in synthesis mixtures of 2,2-dimethyl-3-hydroxypropionaldehyde by RP-HPLC and GC

Summary RP-HPLC and GC methods are described for the determination of the compounds in synthesis mixtures of 2,2-dimethyl-3-hydroxypropionaldehyde (DHPAL). Special attention is paid to the analysis of DHPAL. Conditions for analysis are developed so that no derivatization is needed despite the equilibrium reactions typical of hydroxy aldehydes. Different solvent matrices, pH and sample concentrations are tested in sampling and analysis. Linearity of the calibration lines and precision of the methods are evaluated for all compounds. Detection limits of different compounds are calculated for both methods.     

Transformations of 2,2-dimethyl-2,4-dihydro-3H-pyrrol-3-on-1-oxide derivatives in the Vilsmeier-Haack reaction conditions

Enhydroxylaminones—2,2-dimethyl-2,4-dihydro-3H-pyrrol-3-on-1-oxides were shown to give various chlorinated products in the Vilsmeier-Haack reaction. The general sequence of the reaction steps is determined and the extent of the reaction was shown to be strongly dependent on the substrate structure.     

A stereocontrolled route to the synthesis of (±)-3-amino-2,2-dimethyl-1,3-diphenylpropan-1-ol

Both the diastereomers of (±)-3-amino-2,2-dimethyl-1,3-diphenylpropan-1-ol were synthesized starting from a common intermediate, namely, β-hydroxy oxime 6. Diastereoselective reduction with NaBH₄/TiCl₄ and H₂-Pd/C provided syn- and anti-isomers, respectively. Good overall yield and selectivity were realized using a simple protocol.     

Highly regio- and stereoselective iodocyclization of chiral 3-alkoxycarbonyl-4-propenyl-2,2-dimethyl-1,3-oxazolidines: a computational investigation

The iodocyclization of allylic carbamates 3a and 3b proceeded with high regio- and stereoselection to give 2-oxobicyclo[4.3.0]nonane 5a as the major product. Both the regio- and diastereoselection of the reaction were investigated with the help of molecular mechanics and quantomechanical calculations. The energetic difference between the competing transition states TS-5a and TS-5b is in good agreement with the experimental results and from the calculated transition structures it appears that steric factors direct the discrimination.