1,721,096 research outputs found
Organocatalytic enantioselective methodologies using Morita–Baylis–Hillman carbonates and acetates
No full textLately, the use of Morita–Baylis–Hillman carbonates and acetates in organocatalysis has grown exponentially. Since the pioneering work of Kim and coworkers until the last cycloadditions reported by Barbas, a plethora of new methodologies have been developed. The use of these compounds opens a new gate for the synthesis of C–C or C-heteroatom bonds in an enantioselective fashion and under mild conditions giving access to highly functionalized structures. In this review, we aim to cover these exciting reactions, paying special attention on the nature of the MBH adduct.<br/
Enantioselective methodologies for the synthesis of spiro compounds
No full textThe enantioselective synthesis of spirocycles has been a long time pursued dream for organic chemists. Since the first pioneering efforts of Tamao and coworkers in the enantioselective construction of spirosilanes, many efforts have been devoted to the development of new and promising asymmetric methodologies. Remarkably, with the advent of organocatalysis the number of methodologies has been highly increased. The aim of this tutorial review is to summarize the last trends and developments reported in the literature in the enantioselective synthesis of spirocompounds
Merging transition-metal activation and aminocatalysis
No full textIn this review the principal enantioselective methodologies merging transition-metal catalysis and aminocatalysis are disclosed.1 Introduction2 Transition-Metal and Enamine Catalysis3 Transition-Metal and Iminium Catalysis4 Transition-Metal Catalysis and Organocascade (Iminium/Enamine) Activation5 Conclusions and Perspective
Enantioselective methodologies using N-carbamoyl-imines
No full textNucleophilic addition to carbon–nitrogen double bonds (imines) represents one of the most common strategies for the synthesis of amine derivatives. In order to circumvent the problem associated with low reactivity of imines in nucleophilic addition, various imines with electron-withdrawing groups at nitrogen have been studied, and many of them were successfully applied in asymmetric methodologies. Especially N-carbamoyl imines were found to be useful in the enantioselective synthesis of various organic compounds, due to their increased reactivity toward nucleophiles as well as limited difficulties connected with the removal of the carbamoyl moiety in target molecules. The aim of this review is to cover enantioselective methods based on N-carbamoyl imines, focusing on synthetically useful protocols.<br/
En route to new chiral ferrocene derivatives: dead ends, detours, and avenues
No full textThe enantioselective synthesis of ?-amino-?-ferrocenyl alcohols, a new class of chiral ferrocene derivatives suitable for the elaboration of auxiliaries and ligands for asymmetric synthesis, can be efficiently achieved by the catalytic asymmetric dihydroxylation of 1-ferrocenylalkenes, followed by the regio- and stereoselective substitution of the hydroxy group adjacent to the ferrocene moiety by nitrogen nucleophiles. En route to these compounds, several previously unknown metallocene derivatives such as ?-ferrocenyl epoxides, interannularly cyclopalladated ferrocenyloxazolines, and ?-amino-?-ferrocenyl acids have been obtained. The first examples of an organocatalytic approach to the enantioselective synthesis of chiral ferrocenes are also presented
Enantioselective synthesis of alkyl azaarenes
No full textThis Minireview covers reports on the enantioselective synthesis of alkyl azaarenes since 2014. It deals with the latest achievements on the reactivity of alkyl azaarenes aiming at the preparation of more complex azaarenes containing chiral centers. They rely on the activating properties of the nitrogen atom when opportunely coordinated with a metal complex or Brønsted acid and possibly containing chiral ligands. In addition, conveniently located electron-withdrawing activating functional groups help increase the reactivity of the azaarenes. The same concepts operate in the case of vinyl azaarenes.</p
Improving asymmetric organocatalysts via supramolecular interactions
No full textSince the rediscovery of proline as a catalyst in aldol reaction in 2000 by List, Barbas and Lerner and, soon after, the development of imonium catalysis by D. W. C. MacMillan, the emergence of Organocatalysis as an important instrument in Organic Synthesis is outstanding. Nowadays, one of the most important goals for chemist is the quest for new and more efficient catalysts. One emerging tool for improving existent organocatalysts consists in using additives which interact with the catalysts via supramolecular interactions such as hydrogen bonding. These interactions provide better catalysts in terms of activity and selectivity. The present review aims to cover and discuss the current evolution of this fast growing field
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