Search results for "Organo"
showing 10 items of 1460 documents
Organocatalytic enantioselective synthesis of trifluoromethyl-containing tetralin derivatives by sequential (hetero)Michael reaction–intramolecular n…
2017
The enantioselective synthesis of tetralin derivatives bearing a trifluoromethylated all‐carbon quaternary stereocenter has been accomplished through a synthetic sequence comprising an organocatalytic β‐functionalization of ortho‐1‐trifluoromethylvinyl‐(hetero)aromatic conjugated aldehydes followed by the intramolecular nitrone 1,3‐cycloaddition reaction (INCR). Both nitromethane and N‐Cbz‐hydroxylamine were employed as nucleophiles in the initial organocatalytic conjugate addition step, which provided the chiral information required for the subsequent diastereoselective INCR. Although diastereoselectivity was moderate, good yields and enantioselectivities were, in general, obtained. Intere…
In Vitro Propagation of Sideritis angustifolia Lag.
1987
Summary Hypocotyl, root and cotyledon explants from 30 day old seedlings of Sideritis angustifolia Lag. were cultured on Murashige and Skoog nutrient medium. Organogenesis of roots and shoots was induced with treatments containing BA or KIN in combination with NAA, IAA or 2,4-D, however, those combinations including NAA and BA were optimal. Most regenerated shoots developed roots when transferred to medium without growth regulators. Rooted plantlets were successfully transplanted into soil.
In vitro morphogenesis of grapevine (Vitis vinifera L.) inflorescence primordia, cvs Pinot Noir and Chardonnay
1998
Hormonal regulatory processes controlling in vitro morphogenesis of grapevine inflorescence primordia, excised from latent buds from November to April, were investigated. Cytokinin (benzylaminopurine, BAP), gibberellin (GA3) and auxin (3-indolebutyric acid, IBA) were used at 1 mg/L. BAP induced branch development and flower calyx differentiation. GA3 first promoted the elongation of inflorescence rachis and then promoted flower differentiation up to the formation of normal calyx and calyptra (the fused petals), while anthers and pistils were also present but not functional. IBA did not seem to be directly involved in these morphogenetic processes. After culturing for 6–7 weeks, explants bec…
Supported Organocatalysts as a Powerful Tool in Organic Synthesis
2010
no abstract
ChemInform Abstract: Dual Hydrogen-Bond/Enamine Catalysis Enables a Direct Enantioselective Three-Component Domino Reaction.
2011
A dual system, composed of an enantioselective enamine catalyst and a multiple-hydrogen-bond catalyst achieves the three-component enantioselective aldehyde—nitroalkene—aldehyde domino reaction using either two similar or two different aldehydes.
Macromolecules with groups of high reactivity
1960
Reactions on the reactive groups of macromolecular substances (e.g., cellulose) have long been known, even since before the structures of macromolecules were understood. H. Staudinger carried out numerous reactions with macromolecules, maintaining the degree of polymerization constant, in order to substantiate the macromolecular structure of the substances investigated (polymeric-analogous reactions). During the last fifteen years reactions with macromolecules have been investigated because it was desirable to compare the chemical diversity of low molecular weight compounds with the corresponding chemical diversity of macromolecular compounds. These endeavors bring forth materials which sup…
Novel Applications of Dynamic NMR in Organic Chemistry
2004
Abstract This review article is oriented on NMR applications in studying various dynamic processes of organic molecules. The topic as a whole is too large to be covered exhaustively in one article or by one author. Therefore, the literature searches are limited mainly for the years 1999–2001. Further, many interesting branches joined essentially with organic chemistry such as supramolecular and organometallic chemistry are left outside this article because there exist recent reviews on these topics. Similarly, the theoretical background of dynamic NMR is not included. The nature of dynamic NMR itself is changing with the recent progress in computational possibilities to estimate the differe…
A Simple Organocatalytic Enantioselective Synthesis of Pregabalin
2009
This paper describes a new procedure for the enantioselective synthesis of the important anticonvulsant drug Pregabalin, which shows biological properties as the (S) enantiomer only. The key step of the synthetic sequence is the Michael addition reaction of Meldrum's acid to a nitroalkene mediated by a quinidine derived thiourea. A variety of novel catalysts bearing different groups at the thiourea moiety were synthesized and tested. The most successful catalyst that incorporates a trityl substituent provided up to 75 % ee of (S)-4. The conjugate addition reaction was carried out on a multigram scale with low loadings of catalyst (10 mol-%). Moreover, the catalyst can be recycled showing th…