Palladium can tailor fullerenes : Palladium catalysts enable a number of C? H bond transformations of organo(hydro)fullerene. In addition to anticipated coupling reactions (C? H bond allylation and arylation), an unexpected new C? H bond dimerization reaction and C? C bond‐cleavage reaction were also uncovered.
Functionalized nanodiamonds : Various functional groups have been incorporated into the structures of the naturally occurring diamondoids [1(2)3]tetramantane and [12312]hexamantane (cyclohexamantane), which represent hydrogen‐terminated prism‐shaped nanodiamonds (see picture). The attachment points define the use of these diamond‐like molecules as geometric building blocks for a variety of applications.
Three that matter : Metal acetylides from alkyl propiolates allow C3 homologations with transference of their versatile reactivity profile to products that can then react without further elaboration. Metal‐free acetylides, which are generated by the action of a good nucleophile on the alkyl propiolate, react with suitable electrophiles through different domino reactions to generate skeletal diversity.
Two series of BODIPY dyes with substituents either in the α positions or in the β positions and different conjugation lengths were synthesized by means of iridium‐catalyzed borylation and rhodium‐catalyzed Heck‐type addition (see scheme). The α‐ and β‐substituted series show completely different photophysical properties. BODIPY=boron dipyrrin.
Skillfully attached! meso–meso‐Linked diporphyrins can be efficiently and selectively functionalized with multiple unsaturated carboxylic acid groups through iridium and rhodium catalyses. This post‐modification strategy allows fine‐tuning of energy levels of each porphyrin unit.
Economic and practical advantages are offered by the iron(III)‐catalyzed and air‐mediated tandem coupling/hydroarylation/dehydrogenation of simple readily available aldehydes, alkynes, and amines for the synthesis of 2, 4‐disubstituted quinolines (see scheme).
Enlarged scope by fluorinated mediators : Oxyl radicals are easily formed on boron‐doped diamond (BDD) electrodes and can be exploited for the ortho‐selective coupling to the corresponding biphenols (see scheme). At partial conversion, a clean transformation is achieved that can be applied to electron‐rich as well as fluorinated phenols.
Trifunctional green catalysis : In‐depth characterization shows that oxidant‐free selective oxidation of alcohols by silver nanoparticles on γ‐Al2O3, as a new heterogeneous catalyst, proceeds through cooperation of silver, acid, and base sites (see figure).
Two very distinct chemical reactions, yet a single catalyst : A gold complex promotes the formation of tertiary enamines from a variety of terminal and internal alkynes. Subsequent addition of a terminal alkyne to the reaction mixture affords allenes (see scheme).
Phosphine‐assisted C? H activation of the methyl group of 2‐methylimidazolium compounds led to a series of iridium, rhodium, and palladium complexes of 2‐methyleneimidazolines. Experimental results confirmed that the product of methyl C? H activation is the kinetic product, whereas the aryl C? H activation product is the thermodynamic product (see scheme).
As easy as 1, 2, 3 : A palladium‐catalyzed three‐component coupling generates α,β‐unsaturated γ‐amino acids in a single step (see scheme). The reaction is believed to involve migration of a vinyl substituent to a highly electrophilic palladium carbene. Unlike previous synthetic approaches, this synthesis provides access to γ‐amino acids with non‐natural side chains.
Macrocyclic oxocarbenium ions can be formed from macrolactones that contain benzylic or allylic ether groups through oxidative carbon–hydrogen‐bond activation mediated by 2,3‐dichloro‐4,5‐dicyanoquinone (DDQ). The applicability of this efficient reaction to complex‐molecule synthesis was demonstrated by its use in a brief formal synthesis of neopeltolide (see retrosynthetic scheme) to form the tetrahydropyrone ring.
Theoretically speaking : The mechanistic details associated with the generation and reaction of [CuO]+ species from CuI–α‐ketocarboxylate complexes, especially with respect to modifications of the ligand supporting the copper center, were investigated (see scheme). Theoretical models were used to characterize the electronic structures of different [CuO]+ species and their reactivity in C? H activation and O‐atom transfer reactions.
Efficient route : A novel RhI‐catalyzed regio‐ and stereospecific carbonylation reaction of (1‐alkynyl)cyclopropyl ketones by selective activation of a carbon? carbon σ bond of the cyclopropane ring was demonstrated (see scheme). This method provides a general, efficient, stereoselective route to synthesise 1,3,5‐trisubstituted and 1,3,5,6‐tetrasubstituted 5,6‐dihydrocyclopenta[c]furan‐4‐one with convertible functional groups.
Phosphorus meets carbohydrates : Dimethyl phosphite reacts with ceric(IV) ammonium nitrate (CAN) to give phosphonyl radicals that add to glycals 1 . The derivatives 2 were isolated in high yields and during a subsequent Horner–Emmons reaction underwent an interesting elimination to give 3,6‐dihydro‐2H‐pyrans 3 . The short sequence with simple precursors is applicable to the transformation of hexoses, pentoses, and disaccharides. Bn=benzyl.
Pd doles it out : A palladium‐catalyzed approach to indoles using the title reaction was achieved (see scheme). The oxidant used in this catalytic cycle was O2. Both N‐nonsubstituted and N‐alkyl monosubstituted anilines can be successfully transformed into the corresponding indoles by this method.
Reacting in the 'Ni'ck of time : The title reaction is realized by using an isolated NiII complex ( 1 ). The catalysis tolerates a wide range of important functional groups that are often incompatible with Grignard reagents in cross‐coupling reactions.
Effective devotion : An efficient cobalt‐catalyzed method devoted to the formation of symmetrical biaryls is described avoiding the preparation of organometallic reagents. Various aromatic halides functionalized by a variety of reactive group reagents are employed. Preliminary DFT calculations have shown that the involvement of a CoI/CoIII couple is realistic at least in the case of 1,3‐diazadienes as ligands (FG=functional group).
Triethylamine hydroiodide crystals were formed during Sonogashira reactions; after complete reaction the solution retains a characteristic light color (see picture). Very sluggish Sonogashira reactions of electron‐enriched aryl diiodides have been carried out in high yield in an oxygen‐free, two‐chamber reaction system. The formation of triethylamine hydroiodide crystals was monitored to determine the completion of reaction.
Simple and brilliant : 1‐Substituted 1H‐indole‐2‐carboxylic acids efficiently undergo successive diarylation accompanied by C? H bond cleavage and decarboxylation upon treatment with aryl bromides in the presence of a palladium catalyst system to afford fluorescent 2,3‐diarylindoles. This facile synthetic method provides a highly efficient blue emitter with a quantum yield of 0.97 in the solid state (see scheme).
