Search results for "Annulation"

A new Infraclavicular Landmark-Based Approach to the Axillary Vein as an Alternative Method of Central Venous Cannulation

2016

Purpose: We developed the new technique of the axillary vein catheterization, which is connected with the determination of only two anatomical points of reference for puncture site identification. The primary outcome of this study was to determine the rate of successful catheterizations and the assessment of procedure success rate, depending on cannulation side as well as physician experience. The secondary objective was to evaluate the early complication rate and to determine whether this method can be used in clinical practice. Methods: The methodology of this prospective, cohort study included catheterization of the axillary vein via the infraclavicular approach. All procedures were perf…

Real-time ultrasound-guided infraclavicular axillary vein cannulation: A prospective study in mechanically ventilated critically ill patients.

2016

Purpose: The main purpose of this study was to define the venipuncture and catheterization success rates and early mechanical complication rates of ultrasound-guided infraclavicular axillary vein cannulation. Materials and methods: We performed in-plane, real-time, ultrasound-guided infraclavicular axillary vein catheterizations under emergency and nonemergency conditions in mechanically ventilated, critically ill patients. Results: We performed 202 cannulation attempts. One hundred and twenty-six procedures (62.4%) were performed under emergency conditions. The puncture of the axillary vein was successful in 98.5% of patients, and the entire procedure success rate was 95.1% (95% confidence…

N-Heterocyclic Carbene-Catalyzed Activation of α-Chloroaldehydes: Asymmetric Synthesis of 5-Cyano-Substituted Dihydropyranones

2017

An N-heterocyclic carbene (NHC)-catalyzed asymmetric [4+2] annulation of (E)-2-benzoyl-3-phenylacrylonitriles with α-chloroaldehydes has been developed. The protocol leads to 5-cyano-substituted dihydropyranones in good to excellent yields with excellent diastereo- and enantioselectivities (up to 93% yield, >20:1 d.r. and 99% ee).

Asymmetric Synthesis of Tetrahydrobenzofurans and Annulated Dihydropyrans via Cooperative One-Pot Organo- and Silver-Catalysis

2016

Synthesis : journal of synthetic organic chemistry 48(19), 3207-3216(2016). doi:10.1055/s-0035-1561468

N‐Heterocyclic Carbene Catalyzed [4+2] Annulation of Enals via a Double Vinylogous Michael Addition: Asymmetric Synthesis of 3,5‐Diaryl Cyclohexenones

2017

A strategy for the N-heterocyclic carbene (NHC) catalyzed asymmetric synthesis of 3,5-diaryl substituted cyclohexenones has been developed via oxidative [4+2] annulation of enals and alkenylisoxazoles. It is the first example of using NHC organocatalysis in a double vinylogous Michael type reaction, a challenging but highly desirable topic. This unprecedented protocol affords good yields as well as high to excellent diastereo- and enantioselectivities.

3,4-Dihydro-2H-pyrrole-2-carbonitriles: Useful Intermediates in the Synthesis of Fused Pyrroles and 2,2′-Bipyrroles

2016

Various heterocyclic structures containing the pyrrole moiety have been synthesized from easily accessible 3,4-dihydro-2H-pyrrole-2-carbonitriles in one-pot procedures. 5,6,7,8-Tetrahydroindolizines, 2,3-dihydro-1H-pyrrolizines as well as 6,7,8,9-tetrahydro-5H-pyrrolo[1,2-a]azepines were obtained from these precursors in high yields in an alkylation/annulation sequence. The same conditions were applied in the synthesis of a 5,8-dihydroindolizine, which could easily be transformed to the corresponding indolizine by dehydrogenation. Furthermore, oxidative couplings of 3,4-dihydro-2H-pyrrole-2-carbonitriles with copper(II)-salts furnished 2,2'-bipyrroles as well as 5,5'-bis(5-cyano-1-pyrroline…

Synthesis of [1,2]oxazolo[5,4-e]indazoles as antitumour agents

2013

Abstract A series of 40 derivatives of the [1,2]oxazolo[5,4-e]indazoles ring system have been prepared with good yields using a versatile and convenient route. Annelation of the [1,2]oxazole ring on the indazole-4-one system was achieved by reaction of the corresponding enaminoketones with hydroxylamine hydrochloride. Derivatives of the title ring system were tested by the National Cancer Institute of Bethesda and one of them (13t) showed growth-inhibitor activity against all the 54 human tumour cell lines generally at low micromolar concentrations.

Organocatalytic Asymmetric Synthesis of Trifluoromethylated Tetrahydrocarbazoles by a Vinylogous Michael/Aldol Formal [4+2] Annulation

2018

N-Heterocyclic Carbene Catalyzed Asymmetric Synthesis of Dihydropyranothiazoles­ via Azolium Enolate Intermediates

2017

A highly diastereo- and enantiostereoselective synthesis of bicyclic dihydropyranothiazoles combining a thiazole and δ-lactone skeleton via NHC-catalyzed [4+2] annulation of 5-alkenylthiazolones and α-chloroaldehydes has been developed. The heterocyclic products are formed via azolium enolate intermediates in good yields with high diastereo- and enantistereoselectivities.

Novel [6]- and [7]Helicene-Like Quinones via Mono- and Bidirectional Chromium-Templated Benzannulation of Bridged Binaphthyl Carbene Complexes

2005

A new organometallic approach to novel, functionalised, helicene-like quinones and bisquinones has been developed based on the chromium-templated [3+2+1] benzannulation reaction. The [5]helicene-analogous monocarbene chromium complexes 4, 5, 17 and 19, derived from dibromo-substituted methylene- or silylene-tethered binaphthols 2 and 3, react with various alkynes to give [6]helicene-like quinones 6–13 and 20–29 after oxidative work-up. A rare competition of angular vs. linear annulation is observed for the incorporation of phenylacetylene that affords quinones 21/22 and 28/29. Protection of the phenolic benzannulation product with camphanic acid chloride 14, followed by chromatographic sepa…