1,721,060 research outputs found
A Convenient Synthesis of (E)-Non-3-ene-2,5-dione, an Important Component Isolated from the Fire Bee Trigonia Tataira
No full textCatalysts’ evolution in the asymmetric conjugate addition of nitroalkanes to electron-poor alkenes
Full text linkThe conjugate addition of nitroalkanes to electron-poor alkenes is a widely used process which only in
the late nineties of the last century has efficiently evolved in its asymmetric version. Synthetic protocols
based on chiral organocatalytic methods have been largely exploited for the generation of optically pure
γ-nitro derivatives through carbon–carbon bond formation. Chiral metal–ligand complexes have also
been successfully employed for these conjugate additions, although their use in the synthesis of targeted
bioactive compounds still appears rather limited. Most of the practical applications of the obtained
adducts are based on the easy conversion of the nitro group into a primary amine directed to the preparation
of nitrogen-containing structures. This review aims to provide a journey of the catalyst usage for
the enantioselective conjugate addition of nitroalkanes to electron-poor olefins, from the early attempts
to the latest achievements. The discussion is categorized according to the nature of different catalytic
systems, and a final section reporting selected applications to targeted compounds is provided
Aza-Michael Reaction: Mono- versus Bis-Addition Product
No full textThe aza-Michael reaction is one of the most important reactions in modern organic synthesis since a carbon-nitrogen bond is formed during the reaction.1 Primary amines add to electron poor alkenes that are susceptible to nucleophilic attach to give secondary and tertiary products. The first product formed, the secondary derivative, is a result of a mono-addition reaction. The mono-adduct can react further to give the tertiary derivative.
In this study, the aza-Michael reactions between primary amines and propenoates (Scheme 1) were investigated under environmentally-friendly solventless conditions2 in order to obtain the mono-adduct or the bis-adduct. The reaction conditions were altered so as to maximise the yields of the desired product.
Preliminary results will be presented
Formation of Carbon-Carbon Double Bonds: Recent Developments via Nitrous Acid Elimination (NAE) from Aliphatic Nitro Compounds
No full textAliphatic nitro compounds having an acidic hydrogen in the beta-position, with respect to the nitro group, are prone to undergo the elimination of nitrous acid, mainly under basic conditions, affording a C=C double bond. Until a few decades ago, the literature reported some examples of the application of this elimination as a strategic step in the synthesis of a variety of important targets. However, mainly in the last two decades, this methodology has been largely developed and applied, thus the aim of this review is to report the most important recent improvements
Synthesis of Highly Substituted Phenols from 1,3-Dinitroalkanes
No full textNitroalkanes are one of the most useful class of compounds for the carbon-carbon bond formation. , Recently, the possibility for the nitro-group to act both as electron-withdrawing and leaving group has been exploited for the regioselective synthesis of polisubstituded aromatic systems, such as methyl benzoate and diarylamine derivatives.
Here we wish to report a new, three steps synthesis of polyfunctionalized phenols starting from 1,3-dinitroalkanes (1). The latter compounds can be converted into dinitrocyclohexanols 2 by their reaction with acrolein under basic conditions (neat Al2O3); treatment of 2 with potassium carbonate, followed by acidic work up, gives nitrocyclohexenones 3, which in turn can be converted into substituted phenol (4) by treatment with pheniltrimethylammonium tribromid
Envirocat EPZG® as a New Heterogeneous Catalyst for the Regeneration of Ketones from Their Tosylhydrazones
No full textEnvirocat EPZG® represents a new heterogeneous catalyst for ketones regeneration from their tosylhydrazones. Aldehyde tosylhydrazones were less reactive under these conditions, allowing to perform a selective regeneration of ketone in the presence of both ketone and aldehyde tosylhydrazones
Nitroalkanes as a new source of 2-alkylidene-1,4-diols, in two steps
No full textA variety of 2-alkylidene-1,4-diols have been conveniently prepared, in two steps, by conjugate addition of a nitroalkane to the appropriate enedione derivatives under basic conditions (DBU), followed by chemoselective reduction (LiAlH4/Et2O) of the carbonyl functionalities of the Michael adduct, obtained after elimination of nitrous acid
Nitroalkanes and dimethyl maleate as source of 3-alkyl succinic anhydrides and (E)-3-alkylidene succinic anhydrides
No full textNitroalkanes react with dimethyl maleate giving a tandem Michael addition/elimination of nitrous acid. The obtained (E)-2-alkylidene dimethyl succinates are: (i) reduced to the corresponding 2-alkyl dimethyl succinates which after hydrolysis produce 1,4-dicarboxylic acids that are prone to convert into the corresponding 3-alkyl succinic anhydrides or (ii) hydrolysed to (E)-2-alkylidene-succinic acids that are easily cyclised to (E)-3-alkylidene succinic anhydrides
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