Sonogashira coupling of the ethynyl monocarborane [CB₁₁H₁₁-12-CCH]⁻

Abstract

The Sonogashira cross coupling between the monocarborane cluster 12-ethynylmonocarba-closo-dodecaborate [CB11H11-12-CCH]– and bromoarenes under Pd catalysis has been developed, providing access to aryl carboranyl alkynes in yields of 42–95%. The transformations...

Transition-Metal-Catalyzed C–H Activation Reactions for the Creation and Modification of Organic Fluorophores

“…Palladium-catalyzed cross-coupling reactions have been extensively employed in material chemistry in the synthesis of a wide spectrum of fluorescent molecules. [30][31][32][52][53][54][55][56][57][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75] However, the drawback is the requirement for pre-functionalized starting materials which usually are aryl halides or pseudohalides. 76 Of the aryl halides, aryl chlorides are usually the cheapest and most easily accessible, but they are, at times, poorly active in palladium-catalyzed cross-coupling reactions due to their slower rate of oxidative addition (Scheme 16).…”

Selective Functionalization of Carbonyl Closo-Decaborate [2-B10H9CO]− with Building Block Properties via Grignard Reagents

“…The functionalization pathways of carboranes are quite vast and established; the most recent approach reported direct B–H functionalization of icosahedral carboranes at the most electron-rich boron vertex, that is, the boron vertex with the lowest B–H bond dissociation energy, where a nitrogen-centered radical-mediated hydrogen atom transfer instigated the homolysis of the B–H bond [ 36 ]. Conventionally recognized pathways include Metal-catalyzed cross-coupling reactions for assembling larger molecules via covalently bonded molecular fragments [ 37 ], the Sonogashira [ 38 ], Heck [ 39 ] and Suzuki cross-coupling reactions [ 40 ], the Kumada-Corriu cross-coupling reactions between B-iodo-carboranes and Grignard reagents in the presence of palladium-based catalysts [ 41 ]. A nucleophilic substitution Grignard reaction pathway was also established for B–H bond activation of ortho-carboranes in the absence of any transition metal catalysts; however, the reaction necessitates the presence of two electron-withdrawing aryl groups on the cage carbon atoms [ 42 ].…”

Selective Functionalization of Carbonyl Closo-Decaborate [2-B₁₀H₉CO]¯ with Building Block Properties via Grignard Reagents

“…The functionalization pathways of carboranes are quite vast and established; the most recent approach reported direct B-H functionalization of icosahedral carboranes at the most electron-rich boron vertex, that is, the boron vertex with the lowest B-H bond dissociation energy, where a nitrogen-centered radical-mediated hydrogen atom transfer instigated the homolysis of the B-H bond [36]. Conventionally recognized pathways include Metal-catalyzed cross-coupling reactions for assembling larger molecules via covalently bonded molecular fragments [37], the Sonogashira [38], Heck [39] and Suzuki cross-coupling reactions [40], the Kumada-Corriu cross-coupling reactions between B-iodocarboranes and Grignard reagents in the presence of palladium-based catalysts [41]. A nucleophilic substitution Grignard reaction pathway was also established for B-H bond activation of ortho-carboranes in the absence of any transition metal catalysts; however, the reaction necessitates the presence of two electron-withdrawing aryl groups on the cage carbon atoms [42].…”