8 research outputs found
The determinants of financial flexibility and their implications on the non-financial and non-heavily regulated industries in the Philippines: 1999-2010
This paper intends to identify the determinants of financial flexibility by utilizing the 1999 to 2010 financial data of non-financial and non-heavily regulated publicly listed firms in the Philippines. The generalized method of moments (GMM) was used to discover the significance of the variables determining financial flexibility and the partial adjustment model was used to determine the speed of adjustment of firms in the presence of financial flexibility. The sample consists of 1,188 observations divided into four sectors, which are holding firms, industrials, properties and services. The findings showed that the overall data produced different results as compared to each sector. The most common variables affecting financial flexibility are asset tangibility and firm size. Moreover, as a measurement of financial flexibility, the average speed of adjustment of Philippine firms to achieve their target leverage ratios is about a year
1,3-Dioxa-[3,3]-sigmatropic Oxo-Rearrangement of Substituted Allylic Carbamates: Scope and Mechanistic Studies
International audienceAn unexpected 1,3-dioxa-[3,3]-sigmatropic rearrangement during the treatment of aryl-and alkenyl-substituted allylic alcohols with activated isocyanates is reported. The reorganization of bonds is highly dependent on the electron density of the aromatic ring and the nature of isocyanate used. This metal-free tandem reaction from branched allyl alcohols initiated by a carbamoylation reaction and followed by a sigmatropic rearrangement thus offers a new access to (E)-cinnamyl and conjugated (E,E)-diene carbamates, such as N-acyl and N-sulfonyl derivatives. A computational study was conducted in order to rationalize this phenomenon, and a rearrangement progress kinetic analysis was performed
Microwave-Assisted 1,3-Dioxa-[3,3]-Sigmatropic Rearrangement of Substituted Allylic Carbamates: Application to the Synthesis of Novel 1,3-Oxazine-2,4-dione Derivatives
International audienceIn a first instance, the effect of the microwave irradiation on the 1,3-Dioxa-[3,3]-sigmatropic rearrangement of aryl allylic carbamates was investigated. Under these new conditions, the reaction acceleration was clearly highlighted compared to conventional heating conditions. Depending on the electronic nature of substituents on the aromatic group, this type of rearrangement can be faster with similar or improved yields. Due to this experimental improvement, the diversity of aryl allylic carbamates able to undergo this rearrangement in a reasonable reaction time (30 min.) and with acceptable to high yields was greatly extended. Finally, an original synthetic way involving this microwave-assisted process to access new six-membered heterocyclic structures such as (E)-5-arylidene-1,3-oxazinane-2,4-diones was developed from Morita-Baylis-Hillman (MBH) adducts showing the interest of this molecular rearrangement approach. DFT and Fragment Distortion studies showed in general polar transition structures and connected high deformation and interaction energies with lower activation barriers
Chiral, Sterically Demanding NâHeterocyclic Carbenes Fused into a Heterobiaryl Skeleton: Design, Synthesis, and Structural Analysis
A series
of CuÂ(I), AgÂ(I), and AuÂ(I) complexes incorporating a new
family of imidazopyridin-3-ylidene ligands substituted by a diphenylpyrrolidino
group at N(1) and aryl groups at C(5) has been synthesized and their
structures determined by X-ray diffraction analysis. This structural
study has revealed an extremely high steric protection of the metal
center by the bulky heterobicyclic carbenes, while the inversion at
the exocyclic NÂ(sp<sup>3</sup>) atom provides a remarkable flexibility
Enantioselective Ring-Opening Polymerization of <i>rac</i>-Lactide Dictated by Densely Substituted Amino Acids
Organocatalysis is becoming an important
tool in polymer science
because of its versatility and specificity. To date a limited number
of organic catalysts have demonstrated the ability to promote stereocontrolled
polymerizations. In this work we report one of the first examples
of chirality transfer from a catalyst to a polymer in the organocatalyzed
ring-opening polymerization (ROP) of <i>rac</i>-lactide
(<i>rac</i>-LA). We have polymerized <i>rac</i>-LA using the diastereomeric densely substituted amino acids (2<i>S</i>,3<i>R</i>,4<i>S</i>,5<i>S</i>)-1-methyl-4-nitro-3,5-diphenylpyrrolidine-2-carboxylic acid (<i>endo</i>-<b>6</b>) and (2<i>S</i>,3<i>S</i>,4<i>R</i>,5<i>S</i>)-1-methyl-4-nitro-3,5-diphenylpyrrolidine-2-carboxylic
acid (<i>exo</i>-<b>6</b>), combined with 1,8-diazabicyclo[5.4.0]Âundec-7-ene
(DBU) as a cocatalyst. Both diastereoisomers not only showed the ability
to synthesize enriched isotactic polylactide with a <i>P</i><sub>m</sub> higher than 0.90 at room temperature but also were able
to preferentially promote the polymerization of one of the isomers
(l or d) with respect to the other. Thus, <i>exo</i>-<b>6</b> preferentially polymerized l-lactide, whereas <i>endo</i>-<b>6</b> preferred d-lactide as the substrate. Density functional theory calculations
were conducted to investigate the origins of this unique stereocontrol
in the polymerization, providing mechanistic insight and explaining
why the chirality of the catalyst is able to define the stereochemistry
of the monomer insertion