95 research outputs found
Actuarial Model Assumptions for Australian Inflation, Equity Returns, and Interest Rates
Though actuaries have developed several types of stochastic investment models for inflation, stock market returns, and interest rates, there are two commonly used in practice: autoregressive time series models with normally distributed errors, and autoregressive conditional heteroscedasticity (ARCH) models. ARCH models are particularly suited when there is heteroscedasticity in inflation and interest rate series. In such cases nonnormal residuals are found in the empirical data. This paper examines whether Australian univariate inflation and interest rate data are consistent with autoregressive time series and ARCH model assumptions
Rh-Catalyzed Decarbonylative Coupling with Alkynes via CâC Activation of Isatins
Herein
we report a [5 + 2 â 1] transformation though catalytic
decarbonylative coupling between isatins and alkynes, which provides
a unique way to synthesize 2-quinolinone derivatives. A broad range
of alkynes can be coupled efficiently with high regioselectivity.
This reaction is proposed to go through CâC activation of isatins,
followed by decarbonylation and alkyne insertion. Directing group
(DG) plays a critical role in this transformation. Assisted by the
DG, the CâC cleavage of isatins occurs at room temperature
Highly Selective Mild Stepwise Allylation of <i>N</i>-Methoxybenzamides with Allenes
An efficient RhÂ(III)-catalyzed stepwise ortho allylation
of <i>N</i>-methoxybenzamides <b>1</b> with polysubstituted
allenes is reported. This CâH functionalization involving allenes
is conducted under very mild conditions (â20 °C or room
temperature) and compatible with ambient air and moisture, and it
can be applied to terminal or internal allenes with different synthetically
attractive functional groups. Highly efficient axial chirality transfer
has been realized, yielding optically active lactones
Efficient Benzimidazolidinone Synthesis via Rhodium-Catalyzed Double-Decarbonylative CâC Activation/Cycloaddition between Isatins and Isocyanates
The
first decarbonylative cycloaddition of less-strained cyclic
ketones (isatins) with isocyanates is reported. Initiated by CâC
activation, this distinct [5 â 2 + 2] transformation provides
a rapid entry to access various benzimidazolidinone derivatives, and
a wide range of isocyanates can be efficiently coupled with broad
functional group tolerance. A modified one-pot process combining a
Curtius rearrangement and CâC activation was also achieved
by using acyl azides as the starting materials. A detailed mechanistic
study revealed a surprising double-decarbonylative reaction pathway.
The novel reactivity discovered in this basic research is expected
to shed light on the development of new heterocycle formation methods
through CâC/isocyanate coupling
Efficient Benzimidazolidinone Synthesis via Rhodium-Catalyzed Double-Decarbonylative CâC Activation/Cycloaddition between Isatins and Isocyanates
The
first decarbonylative cycloaddition of less-strained cyclic
ketones (isatins) with isocyanates is reported. Initiated by CâC
activation, this distinct [5 â 2 + 2] transformation provides
a rapid entry to access various benzimidazolidinone derivatives, and
a wide range of isocyanates can be efficiently coupled with broad
functional group tolerance. A modified one-pot process combining a
Curtius rearrangement and CâC activation was also achieved
by using acyl azides as the starting materials. A detailed mechanistic
study revealed a surprising double-decarbonylative reaction pathway.
The novel reactivity discovered in this basic research is expected
to shed light on the development of new heterocycle formation methods
through CâC/isocyanate coupling
Efficient Benzimidazolidinone Synthesis via Rhodium-Catalyzed Double-Decarbonylative CâC Activation/Cycloaddition between Isatins and Isocyanates
The
first decarbonylative cycloaddition of less-strained cyclic
ketones (isatins) with isocyanates is reported. Initiated by CâC
activation, this distinct [5 â 2 + 2] transformation provides
a rapid entry to access various benzimidazolidinone derivatives, and
a wide range of isocyanates can be efficiently coupled with broad
functional group tolerance. A modified one-pot process combining a
Curtius rearrangement and CâC activation was also achieved
by using acyl azides as the starting materials. A detailed mechanistic
study revealed a surprising double-decarbonylative reaction pathway.
The novel reactivity discovered in this basic research is expected
to shed light on the development of new heterocycle formation methods
through CâC/isocyanate coupling
Room-Temperature Synthesis of Trisubstituted Allenylsilanes via Regioselective CâH Functionalization
A RhÂ(III)-catalyzed <i>o</i>-CâH bond functionalization-based
allenylÂation reaction of allenylÂsilanes <b>2</b> with <i>N</i>-methoxyÂbenzÂamides <b>1</b> affords poly-substituted allenylÂsilanes with a wide range
of attractive functional groups in moderate to excellent yields under
very mild conditions (20 °C, compatible with ambient air and
moisture). Those products may be transformed to different products
with attractive structural features. Careful mechanistic studies suggest
the reaction proceeds via <i>o</i>-rhodation, regioselective
insertion, and β-H elimination
Room-Temperature Synthesis of Trisubstituted Allenylsilanes via Regioselective CâH Functionalization
A RhÂ(III)-catalyzed <i>o</i>-CâH bond functionalization-based
allenylÂation reaction of allenylÂsilanes <b>2</b> with <i>N</i>-methoxyÂbenzÂamides <b>1</b> affords poly-substituted allenylÂsilanes with a wide range
of attractive functional groups in moderate to excellent yields under
very mild conditions (20 °C, compatible with ambient air and
moisture). Those products may be transformed to different products
with attractive structural features. Careful mechanistic studies suggest
the reaction proceeds via <i>o</i>-rhodation, regioselective
insertion, and β-H elimination
Hydrogenation and Hydrosilylation of Nitrous Oxide Homogeneously Catalyzed by a Metal Complex
Due to its significant
contribution to stratospheric ozone depletion
and its potent greenhouse effect, nitrous oxide has stimulated much
research interest regarding its reactivity modes and its transformations,
which can lead to its abatement. We report the <i>homogeneously</i> catalyzed reaction of nitrous oxide (N<sub>2</sub>O) with H<sub>2</sub>. The reaction is catalyzed by a PNP pincer ruthenium complex,
generating efficiently only dinitrogen and water, under mild conditions,
thus providing a green, mild methodology for removal of nitrous oxide.
The reaction proceeds through a sequence of dihydrogen activation,
âOâ-atom transfer, and dehydration, in which metalâligand
cooperation plays a central role. This approach was further developed
to catalytic O-transfer from N<sub>2</sub>O to SiâH bonds
BuildSummary: Using a Group-Based Approach To Improve the Sensitivity of Peptide/Protein Identification in Shotgun Proteomics
The target-decoy database search strategy is widely accepted
as
a standard method for estimating the false discovery rate (FDR) of
peptide identification, based on which peptide-spectrum matches (PSMs)
from the target database are filtered. To improve the sensitivity
of protein identification given a fixed accuracy (frequently defined
by a protein FDR threshold), a postprocessing procedure is often used
that integrates results from different peptide search engines that
had assayed the same data set. In this work, we show that PSMs that
are grouped by the precursor charge, the number of missed internal
cleavage sites, the modification state, and the numbers of protease
termini and that the proteins grouped by their unique peptide count
should be filtered separately according to the given FDR. We also
develop an iterative procedure to filter the PSMs and proteins simultaneously,
according to the given FDR. Finally, we present a general framework
to integrate the results from different peptide search engines using
the same FDR threshold. Our method was tested with several shotgun
proteomics data sets that were acquired by multiple LC/MS instruments
from two different biological samples. The results showed a satisfactory
performance. We implemented the method in a user-friendly software
package called <i>BuildSummary</i>, which can be downloaded
for free from http://www.proteomics.ac.cn/software/proteomicstools/index.htm as part of the software suite <i>ProteomicsTools</i>
- âŚ