Multistage Organic Redox Systems—A General Structural Principle

Abstract

A general structural principle for organic compounds that have the capacity for two-stage electron transfer is based on the following reaction sequence:X+CH=CHj,X 5 In this scheme one or both of the entities X may be replaced by Y'. The radical partners in these systems often have very high thermodynamic stability. The choice of the end groups X and Y, (partial) inclusion of n-systems in rings, alteration of the number of vinylene groups,

Recent Advances in the Development of Methods for the Preparation of Functionalized Azulenes for Electrochromic Applications

“…Thus, the reaction of 3a with 4-bromotoluene utilizing this catalytic system gave cross-coupling product 4e in 60% yield (entry 4). Electron-deficient aryl bromides 1-bromo-4-nitrobenzene and 4-bromophenyl methyl ketone and electron-rich bromide 4-bromoanisole also participated in reactions with 3b and 3a catalyzed by Pd 2 (dba) 3 /P(t-Bu) 3 to afford the corresponding cross-coupling products 4b-d and 4f-h in satisfactory yields (entries 1-3 and 5-7, respectively). In general, substrates 3a and 3b undergo efficient reactions with a variety of aryl bromides under the palladium catalysis conditions.…”

“…Stille cross-coupling reactions of azulenyltin compound 3b with 4-bromo-or 4-iodotoluene Cross-coupling reactions of organotin compounds 3a and 3b with several aryl bromides promoted by Pd 2 (dba) 3 /P(tBu) 3 under the optimized conditions generate adducts in modestly high yields (Scheme 3 and Table 2). Thus, the reaction of 3a with 4-bromotoluene utilizing this catalytic system gave cross-coupling product 4e in 60% yield (entry 4).…”

“…In general, substrates 3a and 3b undergo efficient reactions with a variety of aryl bromides under the palladium catalysis conditions. [(n-Bu) 3 Sn a The reactions of 3b with 4-bromo-or 4-iodotoluene were carried out at reflux for 24 h using 10 mol% Pd catalyst, a phosphine ligand (Pd/P = 1:2), and CsF (2.2 equiv) as indicated.…”

“…The formation of 5 is ascribed to an aryl-phenyl exchange process involving the triphenylphosphine ligand in the initial intermediate formed by the oxidative addition of palladium(0) to the aryl halide. 18 However, the substitution of Pd(PPh 3 ) 4 with Pd 2 (dba) 3 (dba = dibenzylideneacetone)/tri-tert-butylphosphine [P(t-Bu) 3 ] in the catalytic protocol caused a significant increase in the efficiency of the formation of the desired cross-coupling product 4a (entry 2).…”

An investigation of anthraquinone-catalysed alkaline pulping via component modeling and electron spin resonance experiments

“…However, the nature of the species formed when AQ is reduced in alkaline solutions is far from clear (3). Although the +J 0-red color of alkaline reduced AQ solutions has been ascribed to the dianion, AQ2-(5,6), one might also expect the semiquinone anion radical (AQ.-) to The picture is further complicated by the variety of absorb light in the visible region (7)(8)(9)(10). The anion solvents used in previous experimental work.…”