Illuminating Lewis acidity strength

In this issue of Chem, Baumgartner, Caputo and co-workers describe a simple naked-eye litmus test for the determination of Lewis acid strength. This technique is based on fluorescence via highly tunable, luminescent phosphole oxide Lewis basic probes

Enantioselective main group catalysis: modern catalysts for organic transformations

This review highlights a number of recent developments in the field of main group enantioselective catalysis. Many essential transformations can be effected catalytically such as hydrosilylation, hydroamination and hydrogenation reactions, amongst others, in an asymmetric fashion using earth abundant s- and p-block elements such as calcium, strontium, boron and aluminum. Recent work in this area has shown that these systems are not only active in catalysis but may also have the potential to compete with transition metal based systems with the reduced cost and toxicity sometimes associated with main group chemistry

Metallfreie Stickstoffaktivierung: Ein neues Kapitel in der Chemie frustrierter Lewis-Paare

Ende des Metallzeitalters: Fortschritte bei der Aktivierung kleiner Moleküle und der Reaktivität von Hauptgruppenverbindungen führen zu der Frage, ob Metallkatalysatoren bei der Distickstoffaktivierung vermieden werden können. Eine bahnbrechende Studie von Stephan und Mitarbeitern deutet darauf hin, dass die metallfreie Aktivierung von N2 mithilfe frustrierter Lewis-Paare in nicht allzu ferner Zukunft möglich sein könnte

A step closer to metal-free dinitrogen activation: a new chapter in the chemistry of frustrated Lewis pairs

The end of the metal age: Recent developments in small-molecule activation and chemical transformations of main-group species pose the question as to whether metal catalysts could be avoided altogether in the activation of dinitrogen. A ground-breaking study by Stephan and co-workers clearly implies that the metal-free activation of N2 with frustrated Lewis pairs may be achievable in the not-too-distant future

Dehydrocoupling routes to element-element bonds catalysed by main group compounds

This Tutorial Review focuses on recent applications of main group compounds in the catalytic synthesis of heteronuclear element–element bonds within the p-block.</p

Shared success - s-block cooperativity toward triazoles

Exploration of the synergistic catalytic activities of a bimetallic s-block system unveils new reactivities of these elements. In this issue of Chem Catalysis, Hevia and co-workers report the discovery of s-block bimetallic cooperative catalysis to afford 1,5-disubstituted 1,2,3 triazoles regioselectivity in good-to-excellent yields

Activation of Diazo Compounds by Fluorinated Triarylborane Catalysts

The diverse applicability of diazo compounds as versatile reagents has enlarged the chemical toolbox in organic synthesis. Over the past few decades, transition-metal-catalyzed diazo compound activation has ignited the classical synthetic methodology via utilizing highly reactive metal carbenoid species. Many reviews have also appeared in the literature that show the advantages and disadvantages of metal-catalyzed activation of diazo compounds. Recently, tris(pentafluorophenyl)borane-mediated diazo activation reactions has remodeled this research area due to the potential for mild, environmentally friendly, metal-free, nontoxic reaction conditions, and the diverse reactivity patterns of boranes towards diazo compounds. In this review, we discuss the reactivity of the boron–diazo precursor adducts with compounds using catalytic and stoichiometric halogenated triarylboranes and, the mechanism of N2 release from the diazo reagent. This generates the reactive carbene species as a key intermediate which can further be exploited for O–H, N–H, S–H, and C–H insertions, azide insertion, carbonate transfer, C–C and C=C bond forming reactions, [2+2] or [2+4] cascade cyclization reactions, annulation reactions, etc

Comparative study of fluorinated triarylalanes and their borane counterparts

The chemistry of Lewis acids, in particular that of triarylboranes, has received unprecedented attention in recent years. Particularly in their role as the Lewis acid component of frustrated Lewis pairs (FLPs), boranes have shown astonishing properties, for example in their ability to bind H2 reversibly. With the current spotlight on main-group chemistry, the heavier aluminum homologs have not yet received much attention. Herein, we provide an overview of the synthesis, properties, and reactivities of fluorinated triarylalanes [Al(ArF)3] in direct comparison to their boron counterparts [B(ArF)3]. In part, the scarcity of studies on fluorinated triarylalanes could be attributed to their shock- and thermal-sensitive nature, which has hampered progress in this field. However, because of their enhanced Lewis acidity compared to their boron complements, they have shown promising behavior in the fields of FLPs and, more recently, frustrated radical pairs (FRPs). They are also capable of effectively catalyzing polymerizations and hydroboration reactions and have proven to be useful as aryl nucleophiles in stochiometric reactions