Antonio J. Martínez-Martínez

Directed ortho-meta′- and meta-meta′-dimetalations: A template base approach to deprotonation

The regioselectivity of deprotonation reactions between arene substrates and basic metalating agents is usually governed by the electronic and/or coordinative characteristics of a directing group attached to the benzene ring. Generally, the reaction takes place in the ortho position, adjacent to the substituent. Here, we introduce a protocol by which the metalating agent, a disodium-monomagnesium alkyl-amide, forms a template that extends regioselectivity to more distant arene sites. Depending on the nature of the directing group, ortho-meta′ or meta-meta′ dimetalation is observed, in the latter case breaking the dogma of ortho metalation. This concept is elaborated through the characterization of both organometallic intermediates and electrophilically quenched products. A network of sodium and magnesium ions helps direct double deprotonation of aryl rings. Bring your own template for deprotonation When manufacturing pharmaceuticals and agrochemicals, chemists need to add substituents to specific carbon sites in hexagonal benzene rings. If theres already a substituent on the ring, it can often direct a base to deprotonate the site next to it. But what if you want the base to attack the site two carbons away? Martínez-Martínez et al. devised a method to do this by taking advantage of the sodium and magnesium counterions associated with their base. These ions form a template that orients the base to attack the more distant site. Science, this issue p. 834

Alkali‐Metal‐Mediated Magnesiations of an N‐Heterocyclic Carbene: Normal, Abnormal, and “Paranormal” Reactivity in a Single Tritopic Molecule

Herein the sodium alkylmagnesium amide [Na4Mg2(TMP)6(nBu)2] (TMP=2,2,6,6-tetramethylpiperidide), a template base as its deprotonating action is dictated primarily by its 12 atom ring structure, is studied with the common N-heterocyclic carbene (NHC) IPr [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]. Remarkably, magnesiation of IPr occurs at the para-position of an aryl substituent, sodiation occurs at the abnormal C4 position, and a dative bond occurs between normal C2 and sodium, all within a 20 atom ring structure accommodating two IPr(2-). Studies with different K/Mg and Na/Mg bimetallic bases led to two other magnesiated NHC structures containing two or three IPr(-) monoanions bound to Mg through abnormal C4 sites. Synergistic in that magnesiation can only work through alkali-metal mediation, these reactions add magnesium to the small cartel of metals capable of directly metalating a NHC.

Templated deprotonative metalation of polyaryl systems : facile access to simple, previously inaccessible multi-iodoarenes

Building blocks for pharmaceutical/electronic materials have been prepared using a templated C–H bond–breaking approach. The development of new methodologies to affect non–ortho-functionalization of arenes has emerged as a globally important arena for research, which is key to both fundamental studies and applied technologies. A range of simple arene feedstocks (namely, biphenyl, meta-terphenyl, para-terphenyl, 1,3,5-triphenylbenzene, and biphenylene) is transformed to hitherto unobtainable multi-iodoarenes via an s-block metal sodium magnesiate templated deprotonative approach. These iodoarenes have the potential to be used in a whole host of high-impact transformations, as precursors to key materials in the pharmaceutical, molecular electronic, and nanomaterials industries. To prove the concept, we transformed biphenyl to 3,5-bis(N-carbazolyl)-1,1′-biphenyl, a novel isomer of 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CPB), a compound which is currently widely used as a host material for organic light-emitting diodes.

Revealing the remarkable structural diversity of the alkali metal transfer agents of the trans-calix[2]benzene[2]pyrrolide ligand

Excellent reagents for transferring their heterocalix[4]arene ligand to f-block organometallic complexes, lithium, sodium and potassium trans-calix[2]benzene[2]pyrrolides have been found to adopt a fascinating series of structures in their own right.