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Metallosalen are privileged complexes that have found important applications in catalysis. In addition, their luminescent properties have also been studied and used for sensing and biological applications. Salen metal complexes can be efficient photosensitizers, but they can also participate to electron transfer processes. Indeed, we have found that commercially available [Al(Salen)Cl] is an efficient photoredox catalyst for the synergistic stereoselective reaction of alkyl aldehydes with different bromo ketones and malonates to give the corresponding enantioenriched α‐alkylated derivatives. The reaction was performed in the presence of a MacMillan catalyst. [Al(Salen)Cl] is able to replace ruthenium complexes, showing that also aluminum complexes can be used in promoting photoredox catalytic reactions. [ABSTRACT FROM AUTHOR]

Stereoselective alkylation of enolates represents a valuable and important procedure for accessing carbon-carbon-bond frameworks in natural and nonnatural product synthesis. Usually, activated electrophilic partners that react through an SN2 mechanism are employed. To overcome the limitations due to reduced reactivity and steric hindrance, SN1-type reactions can be considered a valid and practical alternative. Accessible enolates can be used in stereoselective (diastereo- or enantioselective) reactions with electrophilic carbenium ions, either used as stable reagents or generated in situ from suitable precursors. The results achieved in this active field are summarized in this review. 1 Introduction 2 Alcohols in SN1-Type Reactions with Enolates 2.1 Enantioselective Reactions with Metal Complexes 2.2 Organocatalytic Enantioselective Reactions 3 Alcohols and Alcohol Derivatives in SN1-Type Reactions with Enolates: Enantioselective Reactions with Metal Enolates 4 Isolated Carbenium Ions in SN1-Type Reactions with Enolates: Enantioselective Reactions with Metal Enolates 5 Miscellaneous 6 Conclusion. [ABSTRACT FROM AUTHOR]

Stable diarylcarbenium salts, obtained by the direct coupling of indole or indole derivatives with aryl (or heteroaryl) aldehydes in the presence of a strong organic Brønsted acid, have been employed in the direct alkylation of aldehydes. Excellent enantiomeric excesses and good diastereomeric ratios were obtained with a number of aryl or heteroaryl(3-indolyl)carbenium ions as the highly stable o-benzenedisulfonimide (OBS) salts and with the reaction promoted by the Hayashi-Jørgensen catalyst. A one-pot, three-component, stereoselective alkylation of aldehydes affording the same compounds was also investigated with various aldehydes, indole derivatives, and organocatalysts. The results obtained with the isolated carbenium ions were superior in terms of yields and stereoselectivity. [ABSTRACT FROM AUTHOR]

ABSTRACT Recently, the direct substitution of allylic, benzylic, and tertiary alcohols has been achieved via SN1-type reactions with catalytic amounts of Brønsted or Lewis acids. When a new stereogenic center is formed most of these transformations produce the desired product as a racemate, as these reactions proceed through carbenium ions. The arsenal of activation modes available in organocatalysis can be used to set up suitable reaction conditions in which chiral nucleophiles (enamine ) or chiral electrophiles (iminium , chiral counterion ) can easily be generated. Recently, we have used stabilized carbenium ions, directly available or obtained from the corresponding alcohols, in new organocatalytic SN1-type reactions. The commercially available carbenium ion benzodithiolylium tetrafluoroborate 1 can be used for the straightforward organocatalytic . In this account we will illustrate the application of this methodology in the total synthesis of natural products and the preparation of valuable starting materials. Chirality 26:607-613, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Different substituted ferrocene–guanineconjugates wereprepared, and their electrochemical behavior was investigated. A newapproach for the introduction of ferrocene in guanine’s 9-positionthrough a quite effective SN1-type reaction was disclosed.The electrochemical behavior of the various derivatives can be usedas standard for the quantification and analysis of DNA strands. [ABSTRACT FROM AUTHOR]

The compatibility of indium(III) Lewis acids with water and amines allows their employment in synergistic and cooperative catalysis. Stereoselective organocatalytic SN1-type reactions, in which carbenium ions are generated, are promoted by the presence of indium salts. The peculiar properties of indium salts can be exploited in organocatalysis for the design of water-compatible, benign, green processes. The development of such indium(III)-promoted organocatalytic procedures is the focus of our recent re- search, a summary of which is presented in this article. [ABSTRACT FROM AUTHOR]

In recent years there has been an accelerated rate of development in the field of organocatalysis, with asymmetric organocatalysis now reaching full maturity. The invention of new organocatalytic reactions and the exploration of new concepts now appear in tandem with the application of organocatalytic techniques in the synthesis of natural products and active pharmaceutical ingredients (APIs). After a 'golden rush' in organocatalysis, researchers are now starting to combine different methods, thereby taking advantage of the significant benefits of synergy. Metals are used in combination with organocatalytic processes, thus reaching complexity that is found in nature, where enzymes take advantage of the presence of certain metals to increase the arsenal of organic transformations available. In this Focus review, we illustrate the possibility of a 'happy marriage' between Lewis acids and organocatalytic stereoselective processes. Questions have been raised about the combination of Lewis acids and organocatalysis owing to the presence of water and/or strong bases in these processes. Some Lewis acids have been shown to be compatible with organocatalysis and concepts relating to their use will be illustrated herein. To summarize the fruitful use of Lewis acids in stereoselective organocatalytic processes, we will draw attention to the advantages and selectivity achieved using this method. [ABSTRACT FROM AUTHOR]

The Two Towers, of fruitful collaboration betweEN the teams of Margherita Barbero at Turin University (Turin, left) and Pier Giorgio Cozzi at Bologna University (Bologna, right) came together in their Full Paper on page 337 in describing a simple and affordable procedure for organocatalytic alkylations using stable and easily prepared o ‐ bENzENedisulfonimide salts of (3 ‐ indolyl)methylium carbENium ions. Normally these ions are oftEN used as precursors in organocatalysis and are gENerated in situ. Good yields of up to 95% and high ENantioselectivity of up to 97% accompany the procedure, which works with the commercially available Hayashi–JørgENsEN catalyst and a variety of aldehydes. [ABSTRACT FROM AUTHOR]