Search results for "Wittig reaction"
showing 10 items of 42 documents
2021
The biological activities of shancigusin C (1) and bletistrin G (2), natural products isolated from orchids, are reported along with their first total syntheses. The total synthesis of shancigusin C (1) was conducted by employing the Perkin reaction to forge the central stilbene core, whereas the synthesis of bletistrin G (2) was achieved by the Wittig olefination followed by several regioselective aromatic substitution reactions. Both syntheses were completed by applying only renewable starting materials according to the principles of xylochemistry. The cytotoxic properties of shancigusin C (1) and bletistrin G (2) against tumor cells suggest suitability as a starting point for further str…
Synthesis of fluorinated drimanes. Preparation of 9αF-drimenin
2003
Abstract A stereoselective approach to the 9α-fluorinated analogue of the natural drimane sesquiterpene drimenin starting from β-ionone is described. β-Ionone is transformed into a bicyclic β-cetoester from which 9αF-drimenin is prepared through stereoselective electrophilic fluorination at the C-9 with N -fluorobenzenesulfonimide followed by Wittig methylenation, allylic bromination, bromine-hydroxyl exchange and γ-lactonization.
A facile microsynthesis of 14C-labelled picene
1984
Microscale Wittig olefination of commercially available [7-14C]-benzal dehyde of high specific radioactivity with aryl bromomethyl phosphonium salt and subsequent oxidative photocyclisation affords pure 14C-labelled picene in efficient yield.
ChemInform Abstract: Thermal 1,6-Electrocyclization Reactions of Acceptor-Substituted 2,3-Divinyl-1H-indoles Yielding Functionalized Carbazoles.
1990
Three new synthetic procedures for and thermal 1,6-electrocyclizations of acceptor-substituted 2,3-divinyl-1H-indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)-catalyzed coupling and Wittig procedures.
Wittig-Olefinierung zu neuen donor- und akzeptor-substituierten 3-Vinylindolen: Optimierte Syntheseverfahren
1989
The optimized Wittig reaction of selectively functionalized 3-acylindoles yield new, and for Diels-Alder reactions highly reactive donor- and acceptor substituted 3-vinylindoles, respectively.
A Straightforward Electroactive π-Extended Tetrathiafulvalene (exTTF) Building Block
2012
The synthesis and X-ray structure of a new and readily available exTTF derivative (6) bearing a methyltriphenylphosphonium bromide moiety as a new building block for the construction of electroactive molecules is reported. The phosphonium salt 6, which was prepared in one step from 2-hydroxymethyl-exTTF as a stable yellow solid in 84 % yield, efficiently undergoes Wittig olefination reactions with a variety of aldehydes to predominantly form the E isomer. Electronic spectra and cyclic voltammetry of the novel compounds reveal the electronic communication between the electroactive units.
The dianion of [2.2.2]paracyclophene; a 20 π-perimeter species?
1986
Abstract A new synthesis of [2.2.2]paracyclophene (1) is presented on reduction,(1) forms a stable dianion which is neither diatropic. nor paratropic. The apparent high symmetry of the dianion and the observed NMR chemical shifts are best explained by a rapid interconversion of a series of C 2-conformers.
Thermal 1,6-Electrocyclization Reactions of Acceptor-Substituted 2,3-Divinyl-1H-indoles Yielding Functionalized Carbazoles
1990
Three new synthetic procedures for and thermal 1,6-electrocyclizations of acceptor-substituted 2,3-divinyl-1H-indoles leading to functionalizing carbazoles are described. The scope and limitations as well as some mechanistic aspects of the methodologies are discussed. The key strategies employed include Pd(II)-catalyzed coupling and Wittig procedures.
Synthesis and Antioxidative Properties of 1,2,3,4-Tetrahydropyridine Derivatives with Different Substituents in 4-Position
2022
Natural products are an excellent source of inspiration for the development of new drugs. Among them, betalains have been extensively studied for their antioxidant properties and potential application as natural food dyes. Herein, we describe the seven-step synthesis of new betalamic acid analogs without carboxy groups in the 2- and 6-position with an overall yield of ~70%. The Folin–Ciocalteu assay was used to determine the antioxidant properties of protected intermediate 21. Additionally, the five-step synthesis of betalamic acid analog 35 with three ester moieties was performed. Using NMR techniques, the stability of the obtained compounds towards oxygen was analyzed.
Efficient Stereoselective Synthesis of Boron L-Amino Acid Derivatives Using Wittig and Borylation Reactions
2015
The stereoselective synthesis of a new classes of boronato- or trifluoroborato aminoacids and peptides was described using Wittig and C-H iridium borylation as key reactions. A trifluoroborato-thio...