We present herein an unconventional tandem 3,3-sigmatropic rearrangement/2 + 2 cycloaddition of simple dipropargylphosphonates to deliver a range of bicyclic polysubstituted cyclobutenes and ...cyclobutanes under Ag/Co relay catalysis. An interesting switch from allene-allene to allene-alkyne cycloaddition was observed based on the substitution of the substrates, which further diversified the range of compounds accessible from this practical method. Significantly, preliminary biological screening of these new compounds identified promising candidates as suppressors of cellular proliferation.We present herein an unconventional tandem 3,3-sigmatropic rearrangement/2 + 2 cycloaddition of simple dipropargylphosphonates to deliver a range of bicyclic polysubstituted cyclobutenes and cyclobutanes under Ag/Co relay catalysis. An interesting switch from allene-allene to allene-alkyne cycloaddition was observed based on the substitution of the substrates, which further diversified the range of compounds accessible from this practical method. Significantly, preliminary biological screening of these new compounds identified promising candidates as suppressors of cellular proliferation.
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IJS, KILJ, NUK, UL, UM, UPUK
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•Various amorphous silica-alumina composites were synthesized by hydrolytic method.•Amorphous silica-alumina composite was revealed an efficient solid acid for SRD.•A stable ...bifunctional catalyst with >99% DME conversion and H2 yield was obtained.•DME hydrolysis was revealed the rate-limiting step for two-step reactions of SRD.
In this work, we demonstrate that the amorphous silica-alumina composite (ASA) is an efficient solid acid for the steam reforming of dimethyl ether (SRD). Thus, a series of ASA with different Si/Al molar ratios was synthesized via the modified hydrolytic method by using Al(NO3)3·9H2O and/or NaAlO2 as Al precursor and tetraethoxysilane as Si precursor, respectively. Irrespective of the synthesis conditions, all of ASA composites were in an amorphous nature. However, both the acidity and the surface area were significantly affected by the synthesis conditions, the extent of which depends on the specific precursor and Si/Al molar ratios. The ASA physically mixed with a commercial Cu/ZnO/Al2O3 was investigated as a bifunctional catalyst for SRD under the conditions of P=0.1 MPa and gas hourly space velocity of 4000 h−1. Results indicate that both the conversion of dimethyl ether (DME) and the hydrogen yield were strongly dependent on the acidic property of ASA and the ASA to Cu/ZnO/Al2O3 ratios. Following the two-step consecutive mechanism of SRD, the catalytic results were well explained based on the acidic property of ASA, and the synergetic effect between the two catalytic functions was found to play a crucial role in determining the activity and stability of the bifunctional catalyst. Moreover, the DME hydrolysis was revealed to be the rate-limiting step for SRD reactions in the case of ASA as an acidic catalyst. By optimizing the synthesis conditions of ASA and the composition of the bifunctional catalyst, greater than 99% of DME conversion and hydrogen yield was achieved, and was kept for a time on stream of 66 h without an observable decrease. Thus, ASA is a very efficient solid acid for SRD.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Urolithiasis is a global disease with a high incidence and recurrence rate, and stone composition is closely related to the choice of treatment and preventive measures. Calcium oxalate monohydrate ...(COM) is the most common in clinical practice, which is hard and difficult to fragment. Preoperative identification of its components and selection of effective surgical methods can reduce the risk of patients having a second operation. Methods that can be used for stone composition analysis include infrared spectroscopy, X-ray diffraction, and polarized light microscopy, but they are all performed on stone specimens
after surgery. This study aimed to design and develop an artificial intelligence (AI) model based on unenhanced computed tomography (CT) images of the urinary tract, and to investigate the predictive ability of the model for COM stones
preoperatively, so as to provide surgeons with more accurate diagnostic information.
Preoperative unenhanced CT images of patients with urinary calculi whose components were determined by infrared spectroscopy in a single center were retrospectively analyzed, including 337 cases of COM stones and 170 of non-COM stones. All images were manually segmented and the image features were extracted, and randomly divided into the training and testing sets in a ratio of 7:3. The least absolute shrinkage and selection operation algorithm (LASSO) was used to construct the AI model, and classification of the training and testing sets was carried out.
A total of 1,218 radiomics imaging features were extracted, and 8 features with non-zero coefficients were finally obtained. The sensitivity, specificity and accuracy of the AI model were 90.5%, 84.3% and 88.5% for the training set, and 90.1%, 84.3% and 88.3% for the testing set. The area under the curve was 0.935 for the training set and 0.933 for the testing set.
The AI model based on unenhanced CT images of the urinary tract can predict COM and non-COM stones
preoperatively, and the model has high sensitivity, specificity and accuracy.
Abstract
Diastereo- and enantioselective N-heterocyclic carbene catalyzed 1-azadiene Diels–Alder reactions of (
E
)-2-styrylbenzothiazoles with α-chloro aldehydes are reported. This annulation ...strategy provides an efficient access to medicinally important dihydrobenzothiazolopyridin-1-ones in good to excellent yields (44–97%) with very good to excellent stereoselectivities (up to 9:1 dr, 98% ee) and tolerates quite a range of substituents.
An N-heterocyclic carbene catalyzed activation of α,β-unsaturated
N
-acyltriazoles is described. The
in situ
generated α,β-unsaturated acylazolium intermediates allowed an enantioselective formal 3+3 ...cycloaddition with 1,3-dicarbonyl compounds. The resulting dihydropyranones are formed in good to excellent yields and with high enantioselectivities.
Employing the NHC-catalyzed activation of α,β-unsaturated
N
-acyltriazoles an efficient enantioselective synthesis of dihydropyranones
via
a formal 3+3 cycloaddition with 1,3-dicarbonyl compounds is described.
An NHC-catalyzed regio- and stereoselective Mannich/lactamization domino reaction of
N
-(benzothiazolyl)imines with α-chloroaldehydes has been developed. This new protocol provides a facile approach ...for the asymmetric synthesis of benzothiazolo-pyrimidinones and a pyrrolo1,2
-a
indolone in moderate to good yields (34-78%) and excellent stereoselectivities (87-99% ee, up to >20 : 1 d.r.).
An NHC-catalyzed regio- and stereoselective Mannich/lactamization domino reaction of
N
-(benzothiazolyl)imines with α-chloroaldehydes has been developed.
An NHC-catalyzed regio- and stereoselective Mannich/lactamization domino reaction of
N
-(benzothiazolyl)imines with α-chloroaldehydes has been developed.
An NHC-catalyzed regio- and stereoselective ...Mannich/lactamization domino reaction of
N
-(benzothiazolyl)imines with α-chloroaldehydes has been developed. This new protocol provides a facile approach for the asymmetric synthesis of benzothiazolo-pyrimidinones and a pyrrolo1,2
-a
indolone in moderate to good yields (34–78%) and excellent stereoselectivities (87–99% ee, up to >20 : 1 d.r.).
An NHC-catalyzed regio- and stereoselective Mannich/lactamization domino reaction of N-(benzothiazolyl)imines with alpha -chloroaldehydes has been developed. This new protocol provides a facile ...approach for the asymmetric synthesis of benzothiazolo-pyrimidinones and a pyrrolo1,2-aindolone in moderate to good yields (34-78%) and excellent stereoselectivities (87-99% ee, up to >20 : 1 d.r.).
An NHC-catalyzed Michael/Michael/esterification domino reaction
via
homoenolate/enolate intermediates for the asymmetric synthesis of tetrasubstituted cyclopentanes bearing four contiguous ...stereocenters is described. A variety of α,β-unsaturated aldehydes and 2-nitroallylic acetates react well with good domino yields and high stereoselectivities.
An NHC-catalyzed Michael/Michael/esterification domino reaction
via
homoenolate/enolate intermediates for the asymmetric synthesis of tetrasubstituted cyclopentanes is described.
An NHC-catalyzed Michael/Michael/esterification domino reaction viahomoenolate/enolate intermediates for the asymmetric synthesis of tetrasubstituted cyclopentanes bearing four contiguous ...stereocenters is described. A variety of alpha , beta -unsaturated aldehydes and 2-nitroallylic acetates react well with good domino yields and high stereoselectivities.
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