Search results for "domino"

Toward an understanding of the selectivity in domino reactions. A DFT study of the reaction between acetylenedicarboxylic acid and 1, 3-Bis(2-furyl)p…

2000

The mechanism of the domino reaction between acetylenedicarboxylic acid and 1,3-bis(2-furyl)propane has been theoretically studied in the framework of density functional theory. This domino process comprises two consecutive cycloaddition reactions: the first one is initialized by the nucleophilic attack of the C5 position of the furan ring to a conjugate position of acetylenedicarboxylic acid to give a zwitterionic intermediate, which by a subsequent ring-closure process affords an oxanorbornadiene intermediate. The second reaction is an intramolecular concerted cycloaddition of this intermediate to give the final dioxapentacyclic adduct. For the second cycloaddition, which corresponds to t…

ChemInform Abstract: Electroorganic Synthesis of Nitriles via a Halogen-Free Domino Oxidation-Reduction Sequence.

2016

A direct electroorganic sequence yielding nitriles from oximes in undivided cells is reported. Despite the fact that intermediate nitrile oxides might be formed, the method is viable to prepare benzonitriles without substituents ortho to the aldoxime moiety. This constant current method is easy to perform for a broad scope of substrates and employs common electrodes, such as graphite and lead.

New Tetracyclic Ring System of Biological Interest Indolo[3,2-e][1,2,3]triazolo[1,5-a]pyrimidine through domino reactions of 2-azidoindole

2003

Organocatalytic Domino Oxa-Michael/1,6-Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds.

2016

An asymmetric organocatalytic domino oxa-Michael/1,6-addition reaction of ortho-hydroxyphenyl-substituted para-quinone methides and isatin-derived enoates has been developed. In the presence of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4-phenyl-substituted chromans bearing spiro-connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee).

W sieci (obrazów, intryg i spisków) - na marginesie literackiej reprezentacji XIX wieku w prozie "Dominový efekt" Václava Vokolka

2023

The subject of this article is an analysis of the representation of the nineteenth century in Václav Vokolek’s multithreaded prose work Dominový efekt. The work can be regarded as a specific continuation of the work Cesta do pekel, especially if the pictorial perspective and the conviction that humanity is in a network of secret organisations, conspiracies and, nowadays, various systems are regarded as common points. In this text, the focus is mainly on the reconstruction of the figure of Ernst Gustav Doerell, a 19th- century landscape painter of Northern Bohemia, whose paintings reflected the changes taking place in the natural landscape of the region. Using the historical prototype in par…

Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael-Domino Michael/Aldol Reaction.

2022

A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee). peerReviewed

N-Heterocyclic Carbene Catalyzed Quadruple Domino Reactions through α,β-Unsaturated Acyl Azolium Intermediates : Asymmetric Synthesis of Cyclopenta[c…

2018

An N‐heterocyclic carbene catalyzed domino sequence via α,β‐unsaturated acyl azolium intermediates has been developed. This strategy provides a convenient enantioselective route to functionalized tricyclic coumarin derivatives and cyclopentanes. DFT studies and control experiments were performed to gain better insight into the reaction mechanism. peerReviewed

Pelvic floor and abdominal muscle cocontraction in women with and without pelvic floor dysfunction: a systematic review and meta-analysis

2019

There is an ongoing discussion regarding abdominal muscle (AbM) and pelvic floor muscle (PFM) synergism. Therefore, this study aimed to investigate the cocontraction between AbMs and PFMs in women with or without pelvic floor dysfunction (PFD). The following databases were searched up to December 21, 2018: MEDLINE, EMBASE, LILACS, PEDro and CENTRAL. We included any study that assessed the cocontraction between PFMs and AbMs in women with and without PFD. Two reviewers independently screened eligible articles and extracted data. The outcomes were extracted and analyzed as continuous variables with random effect models. Twenty studies were included. A meta-analysis did not show differences in…

Amputación abdominoperineal extraelevadora en posición prono

2014

The Miles operation is every day more in the limelight. The abdominoperineal resection compared to anterior resection results in increased rate of circumferential resection margin (CRM) infiltration, increased iatrogenic tumor perforation rate and poorer quality of the mesorectum. These worse results may be caused by excessive dissection between the distal mesorectum and the plane of the levator ani and the consequent "resection waist" or "cone" effect in the specimen. A wider excision of the pelvic floor muscles, known as extraelevator abdominoperineal resection (ELAPE), would provide a "cylindrical" specimen which would hypothetically reduce the risk of tumor perforation and CRM infiltrat…

Impact of surgeon organization and specialization in rectal cancer outcome.

2001

Purpose The present study was designed to assess the differences in the outcome of patients with rectal cancer treated by a group of surgeons before and after being organized as a Coloproctology Unit at the same University Department of Surgery. Methods Comparison of two periods of rectal cancer surgery: I (1986–91) and II (1992–95). Period I: 94 patients were operated on by 14 general surgeons. Period II: 108 patients were operated on by only 4 surgeons of the same group organized as a Colorectal Surgery Unit after visiting referral centres abroad, adopting techniques such as total mesorectal excision (TME) for middle and low rectal cancer and washout of rectal stump. Mean follow-up during…