Cyclopropanone equivalents. Formation of 1-pyrrolizidione by a dicyclopropyl imine rearrangement.

A dicyclopropyl ketimine may be formed by the addition of cyclopropyllithium to 1-cyano-1-piperidinocyclopropane. Rearrangement of the ketimine takes place under acid catalysis to form 1-pyrrolizidinone.     

Asymmetric reduction of 2-chloroacrylic acid to (S)-2-chloropropionic acid by a novel reductase from Burkholderia sp. WS

Burkholderia sp. WS has a novel enzyme that catalyzes the asymmetric reduction of 2-chloroacrylic acid to yield (S)-2-chloropropionic acid, which is used as a building block for the synthesis of aryloxyphenoxypropionic acid herbicides. NADPH is required as a co-substrate for this reaction.     

Photolysis of 2-piperidino- and 2-morpholino-3-methoxy-1,4-naphthoquinones

PMR and¹³C NMR spectroscopy was used to establish the structure of the primary products of the photolysis of 2-piperidino- and 2-morpholino-3-methoxy-l, 4-naph-thoquinones. A scheme for the subsequent dark transformations of these compounds is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 709–713, March, 1991.     

The mechanism in the elimination kinetics of 2-chloropropionic acid in the gas phase

The elimination kinetics of 2-chloropropionic acid have been studied over the temperature range of 320–370.2°C and pressure range of 79–218.5 torr. The reaction in seasoned vessel and in the presence of the free radical suppressor cyclohexene, is homogeneous, unimolecular, and obeys a first-order rate law. The dehydrochlorination products are acetaldehyde and carbon monoxide. The rate coefficient is expressed by the following Arrhenius equation: log k₁(s^?1) = (12.53 ± 0.43) – (186.9 ± 5.1) kJ mol^?1 (2.303RT)^?1. The hydrogen atom of the carboxylic COOH appears to assist readily the leaving chloride ion in the transition state, suggesting an intimate ion pair mechanism operating in this reaction.     

Generation of synthetic equivalents of benzdiynes from benzobisoxadisiloles

Linear and angular benzobisoxadisiloles 14 and 16 can serve as the precursors for stepwise generations of the syntetic equivalents of 1,4- and 1,3-benzdiynes. Benzynes generated were trapped as [4+2] cycloaddition products. Two identical or different rings can be fused to the benzdiyne equivalents. Highly substituted arenes were obtained by removing the oxygen bridges from the furan adducts. The synthesis of naphthoxadisilole 28, which can serve as the precursor of 2,3-naphthyne, is also described.     

Synthesis of PPAR agonist via asymmetric hydrogenation of a cinnamic acid derivative and stereospecific displacement of (S)-2-chloropropionic acid

The synthesis of the peroxime proliferator activated receptor (PPAR) alpha,gamma-agonist (1) was accomplished with high enantio- and diastereoselectivity by employing an asymmetric hydrogenation strategy, of an alpha-alkoxy cinnamic acid derivative, to set the C-2 chiral center. A diastereospecific S(N)2 displacement under mild basic conditions established the C-10 stereochemistry without any detectable racemization of the two epimerizable chiral centers.     

Protection by food-derived antioxidants from UV-A1-induced photodamage, measured using living skin equivalents

In a study of biomarkers of ultraviolet-A1 radiation (UV-A1)-induced skin damage, living skin equivalent cultures (LSE) were treated with the antioxidants hesperetin and quercetin-3-glucoside and irradiated with 25 or 50 J/cm2 UV-A1. Changes in the following biomarkers were measured; Interleukin 1-alpha (IL-1alpha), Heme Oxygenase-1 (HO-1), TdT-mediated dUTP nick end labeling (TUNEL) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). IL-1alpha and HO-1 were analyzed by real-time PCR, Western blot, enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. TUNEL and 8-OHdG were determined by (immuno)histochemical techniques. Sections were stained with hematoxylin and eosin (H&E). UV-A1 induced keratinocyte and fibroblast vacuolation and nuclear pyknosis, intense TUNEL staining of fibroblasts and increased staining of cells and nuclei for 8-OHdG. Lesser or marginal increases in intensity followed staining for HO-1 and IL-1alpha. The IL-1alpha increase was confirmed by ELISA assays of the medium supernatants. Hesperetin and quercetin-3-glucoside reduced changes in H&E, 8-OHdG, TUNEL and IL-1alpha. Quercetin-3-glucoside reduced the amount of IL-1alpha in LSE media. These observations support the use of the selected biomarkers to monitor UV-A1 damage and provide evidence that dietary ingredients could reduce ultraviolet-A radiation-induced damage.     

Near-infrared radiation induced conformational change and hydrogen atom tunneling of 2-chloropropionic acid in low-temperature Ar matrix

Former assignments of the matrix-isolation infrared (MI-IR) spectrum of 2-chloropropionic acid are revised with the help of near-infrared (NIR) laser irradiation induced change in conformer ratios. This method allows not only the unambiguous assignment of each band in the MI-IR spectrum to the two trans (Z) and the cis (E) conformers but also the assignment of the spectral bands to different matrix sites. The tunneling decay of the higher-energy cis conformer prepared from both trans conformers in different sites is also investigated. It is shown that the tunneling decay time is very sensitive to the matrix site, especially if the in situ prepared high-energy conformer has a strained geometry in the matrix cage. The analysis shows that the kinetics of some cis → trans back conversion processes cannot be fitted by a single exponential decay. The possible reasons of this observation are examined and discussed. The present and former results clearly show that, in addition to tunneling processes, the decay rates strongly depend on solid-state effects. Therefore, simple theoretical predictions of decay rates, which do not take into account the solid-state effects, can only be compared to experimental observations only if experimentally proven that these effects do not significantly affect the experimentally measured tunneling rates.     

A study of 2-piperidino-1-ethanol and its derivatives as antimicrobial additives to oils

Some derivatives of 1-hydroxy-2-pyperidinoethane were studied as antimicrobial additives to lubricant oils.     

The Chemistry of Small Ring Compounds. Part 231 Improved Synthesis of Cyclopropanone and Some 1-Substituted Cyclopropanols

Cyclopropanone, the simplest member of the cyclic ketones, has fascinated organic chemists for decades. Although its (attempted) synthesis was reported as early as 1890², its first preparation dates back to 1932, when Lipp³ et al. succeeded in isolating 1,1-dihydroxycyclopropane from the reaction of diazomethane with an excess of ketene. Much later, in 1966, Schaafsma¹ succeeded in isolating the free ketone prepared iron the same reagents by using liquid propane as the solvent. At about the same time, the (dissolved) ketone was also characterized by Turro and Hammond.⁵ Cyclopropanone undergoes a rapid reaction with all types of nucleophiles^6,7, and many of the resulting 1-substituted     

Glyoxylic acid and MP-glyoxylate: efficient formaldehyde equivalents in the 3-CC of 2-aminoazines, aldehydes, and isonitriles

[reaction: see text] Glyoxylic acid, either in solution or immobilized on MP-carbonate (MP-glyoxylate), participates in an uncatalyzed 3-CC with 2-aminoazines and isonitriles to afford novel 2-unsubstituted-3-amino-imidazoheterocycles. MP-glyoxylate serves as a particularly efficient and experimentally convenient formaldehyde equivalent and readily liberates products through decarboxylation/self-release from the resin. These examples furthermore constitute the first application in which MP-CO3 serves as a solid support for transformations involving carboxylic acids.     

1,2,4-Oxadiazoles from cycloreversions of oxadiazabicyclo[3.2.0]heptenes: 1-azetines as thiocyanate equivalents

1,3-Dipolar cycloaddition of nitrile oxides to 4-aryl-2-alkylthio-1-azetines gave a series of oxadiazabicyclo[3.2.0]heptenes as single diastereoisomers. Heating these cycloadducts in toluene resulted in an overall [2+2]-cycloreversion to give 5-alkylthio-3-aryl-1,2,4-oxadiazoles. In this process, the 1-azetine behaves as a thiocyanate equivalent. When the nitrile oxide substituent was 2-azidobenzene, the azide could be converted into a 1,2,3-triazole giving a (1,2,4-oxadiazolo)-(1,2,3-triazolo)-1,2-disubstituted benzene. 1,2,4-Oxadiazoles are sought after in medicinal chemistry and materials sciences.     

Protonation of acyl anion equivalents generated from acylphosphonates: nonhydride access to the aldehyde oxidation state from the carboxylic acid oxidation state

Acylphosphonates, which are easily available from carboxylic acids, are potent acyl anion precursors and undergo cyanide ion promoted phosphonate-phosphate rearrangement to provide the corresponding acyl anion equivalents as reactive intermediates. The protonation of these acyl anion equivalents furnished cyanohydrin O-phosphates in good yields. For the high yield formation of cyanohydrin O-phosphates from arylphosphonates THF should be used and from alkylphosphonates DME was used.