We report a general protocol for the convergent synthesis of 1,4-dicarbonyl Z-alkenes form alkynes using α-diazo sulfonium triflate and water. The C═O, C═C, C–H bonds are formed under mild conditions with wide range functional groups tolerated. reaction exhibits excellent Z-selectivity complete regioselectivity. resulting can smoothly undergo follow-up conversion to variety heteroaromatic scaffolds. Moreover, also provides facile access corresponding deuterated heteroarenes high level...

Accurately distinguishing the types of tea is great significance to pricing, production, and processing tea. The similarity internal spectral characteristics appearance different greatly limits further research on identification. However, wavelet transform can simultaneously extract time domain frequency features, which a powerful tool in field image signal processing. To address this gap, method for recognition based lightweight convolutional neural network support vector machine...

Alpine meadows are one major type of pastureland on the Tibetan Plateau. However, few studies have evaluated response soil respiration (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) to grazing along an elevation gradient in alpine meadow Here three fenced enclosures were established at elevations (i.e., 4313 m, 4513 and 4693 m) July 2008. We...

Rhodium(III)-catalyzed triple C-H bond activation of aryl enaminones was achieved to access naphtho[1,8-bc]pyrans by oxidative annulation internal alkynes. 1-Naphthols might be formed as the only products, depending on steric and/or electronic environment around aroyl moiety or impact from With propargyl alcohols masked terminal alkynes, underwent rhodium(III)- rhodium(I)-catalyzed alkenyl afford functionalized but-2-ene-1,4-diones. The resultant are highly fluorescent and can further...

Abstract Transition‐metal‐catalyzed alkyl‐Heck‐type cross‐coupling of olefinic C−H bonds has been a challenge in the activation area. Herein, we report FeCl 3 ‐promoted efficient direct cyanoalkylation internal alkenes, that is, ketene dithioacetals, with cycloketone oxime esters via radical C−C bond cleavage under redox‐neutral conditions. With CuCl 2 as catalyst dioxygen atmosphere cyanoalkoxylation same alkenes was achieved. The cyanoalkylated tetrasubstituted alkene products could be...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDiastereoselective Propargylation of .alpha.-Alkoxy Aldehydes with Propargyl Bromide and Zinc. A Versatile Efficient Method for the Synthesis Chiral Oxygenated Acyclic Natural ProductsWen-Lian Wu, Zhu-Jun Yao, Yun-Long Li, Jin-Cui Yi Xia, Yu-Lin WuCite this: J. Org. Chem. 1995, 60, 10, 3257–3259Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1...

The content of tea polyphenols (TP) is one the important indicators for judging quality tea. Accurate and non-destructive estimation technology polyphenol has attracted more attention, which become a key production, identification, grading so on. Hyperspectral imaging fusion spectral analysis image processing technology, been proven to be an efficient predicting content. To make full use spatial features, prediction model based on spectral-spatial deep features extracted using convolutional...

Condensations of the chiral N-ferrocenylethylindoloazepines 4a,b, with aldehydes 5, 13, 19, 29, and 32, led to tetracyclic vinylogous urethanes 6a,b 7, 14a 14b, 21a,c 21b,d, 30a 31a, 30b 31b. Respectively, 6:1, 5:1, 3:1, 1.7:1, 2:1 diastereomeric selections provided intermediates which, on cleavage auxiliary N-substituent subsequent elaboration ring D Aspidosperma Strychnos alkaloids, enantiomerically pure (−)-ψ- (−)-epi-ψ-vincadifformines (1, 2), (+)-ibophyllidine (12), (+)-...

The reactions of the five-membered cyclic osmacarbyne complex, i.e., osmapentalyne, with a complete set coinage metal (Cu, Ag, and Au) complexes have been investigated. Osmapentalyne 1 reacts CuCl or AuCl(PPh3) via its metal–carbon triple bond, leading to formation osmapentalyne-copper(I) chloride adduct 2 osmapentalyne-gold(I)-triphenylphosphine 3, respectively. Moreover, it can react AgOTf in presence 1,10-phenanthroline give osmapentalyne-silver(I)-phenanthroline 4. All compounds...

D-ribo-Phytosphingosine has been synthesized from D-galactose via the key intermediate 5, itself prepared by stereoselective prop-2-ynylation with prop-2-ynyl bromide and zinc, L-lyxo-phytosphingosine D-xylose 18, a CBr4–Ph3P–Zn Wittig reaction debromination. These chiral intermediates, 5 have potential as intermediates for synthesis of other phytosphigosine derivatives.

The hexacyclic ketoester 7, derived from cyclization of racemic minovincine (6), was reduced to two C-19 epimeric alcohols 8 and 9. Stereoelectronically controlled fragmentations corresponding O-sulfonyl derivatives provided, respectively, the enamine 14 and, after oxidation olefin 16, pentacyclic lactam 17 with a brigehead double bond. Formation carbamate, introduction second bond at C-16, conjugate reductive hydroxylation C-20, or hydrogenation, gave title products.

An efficient asymmetric synthesis of conformationally constrained (2S,3S)-piperidinedicarboxylic acid derivatives starting from l-aspartic β-tert-butyl ester and 3-chloro-2-(chloromethyl)-1-propene is described. The key steps involve N-alkylation the aspartic followed by a stereoselective enolate intra­molecular cyclization (>95:5 dr). Various synthetic strategies were explored to achieve cyclopropanation resulting olefin, ­including Simmons-Smith reaction palladium-catalyzed cyclopropanation.

ADVERTISEMENT RETURN TO ISSUEPREVLetterNEXTADDITION / CORRECTIONThis article has been corrected. View the notice.A Biomimetic Synthesis of Pauciflorine A and B SkeletonMartin E. Kuehne Yun-Long LiView Author Information Department Chemistry, University Vermont, Burlington, Vermont 05405Cite this: Org. Lett. 1999, 1, 11, 1749–1750Publication Date (Web):October 22, 1999Publication History Received7 September 1999Published online22 October inissue 1 December...

A new facile route to (2E,4E)-dienals by a double formyl-olefination with arsonium salts has been developed. By this method and other reagents in the key step some lipoxygenase metabolites of arachidonic acid, lipoxin A4 B4 leukotriene B4, have synthesized.

Functionalized 1,3-dienes were efficiently accessed from visible-light-driven, palladium-catalyzed Heck reaction of S,S-functionalized internal vinyl bromides with styrenes under mild conditions. This showcased tolerance a wide array functional groups, afforded the target products in moderate to excellent yields through radical pathway. The resultant diene could be further transformed highly functionalized trisubstituted furan derivatives.

The feasibility of a scheme in which the concentration CO2 gas-liquid solution is directly measured based on PZT piezoelectric-photoacoustic spectroscopy was evaluated. existing device used for measurement gas has several limitations, including prolonged duration, loss gas, and high cost due to degassing component. In this study, we developed measuring order solve problems mentioned above. Using device, how intensity photoacoustic signal changes with demonstrated through experiment. impact...

In the steel coil manufacturing industry, quality of end face is not only related to product itself, but also directly affects equipment safety downstream production lines. Therefore, detection defects has a pivotal position. This paper proposes SCED-Net (Steel Coil End Detection Network) based on latest YOLO series masterpiece YoloX. this paper, by supplementing data augmentation method, combining proposed multi-information fusion module, while introducing focal loss and soft-nms, achieved...

(+)-(R)-1,2-(alpha-(R)-Mesyloxy-beta-dimethyltetramethylene)-ferrocene was synthesized and used as a chiral auxiliary for N-alkylation of methyl 1,2,3,4,5,6-hexahydroazepino[4,5-b] indole-5-xi-carboxylates. Condensation with aldehydes then provided tetracyclic products in diastereomeric ratio at least 97:3. Gentle cleavage acetic acid removed the to give corresponding secondary amines >99% ee. Thus, key intermediates leading mossambine vinblastine could be high enantioselectivity. The...

Predicting urban traffic flow is significant to intelligent transportation systems. Urban data a type of time-series data, which collects the road section or area. So in this paper, we treat prediction as time series problem. The traditional method tackle difficult, because complex influence factors and nonlinear dependencies. Recently, LSTM based network has been widely used model long-term series, but memory typically too small not enough accurately remember facts from past. In using with...