Mechanofluorescent polymer/silsesquioxane composites were prepared by introducing tetraarylsuccinonitrile derivatives, which are mechanically cleaved to generate the corresponding pink carbon-centred radicals that exhibit yellow fluorescence.

We have developed a safe and practical synthetic method for preparing axially chiral diphenyl dicarboxylates using Pd-catalyzed external-CO-free carbonylation with phenyl formate as a CO surrogate. Optimized conditions consisted of axially chiral [1,1′-binaphthalene]-2,2′-diyl ditriflate and its congeners, each easily prepared from commercially available enantiomerically pure diols, Pd(OAc) 2 , 1,3-bis(diphenylphosphino)-propane, ethyldiisopropylamine, and no solvent. To demonstrate the potential utility of these products, this method was conducted on gram-scale and the phenyl ester products were converted to other useful compounds, and both processes were carried out without difficulty.Key words axially chiral dicarboxylate; carbonylation; phenyl formate; carbon monoxide surrogate; palladium; catalysis Axially chiral compounds have found wide applications as ligands and organocatalysts in asymmetric organic reactions.1-5) Their chiral backbones effectively construct an asymmetric environment around the molecules, enabling catalytic transformations, often with high enantioselectivity. A number of biaryl and spirocyclic chiral ligands are commercially available from multiple suppliers, and many recent papers mentioning the development of novel axially chiral ligands and organocatalysts indicate increasing demand and potential of axially chiral compounds for asymmetric catalysis.In the search for highly effective chiral ligands and organocatalysts, [1,1′-binaphthalene]-2,2′-dicarboxylic acid and its derivatives such as esters are attractive axially chiral compounds.6-9) However, most previous methods for the synthesis of the enantiomerically pure dicarboxylic acid and dicarboxylates required multiple tedious steps. [10][11][12][13][14][15][16][17] In addition, many of the methods include time-consuming optical resolution of racemic dicarboxylic acid. Therefore, it is desirable to develop more practical synthetic methods with fewer steps. Since enantiomerically pure 1,1′-bi-2-naphthol is readily available from many suppliers, it would be an efficient starting point in the synthesis of the targeted dicarboxylates (Chart 1). Recently, Hamashima and colleagues reported the synthesis of dicarboxylic acid from 1,1′-bi-2-naphthol via lithiation of [1,1′-binaphthalene]-2,2′-diyl diphosphate followed by carboxylation with carbon dioxide.18) While this method affords dicarboxylic acid in high yield in two steps, the involvement of the strongly basic dilithiated intermediate might prove unmanageable with more complex substrates. As another route to [1,1′-binaphthalene]-2,2′-dicarboxylates from 1,1′-bi-2-naphthol, Takaya and colleagues previously reported the Pd-catalyzed alkoxycarbonylation of [1,1′-binaphthalene]-2,2′-diyl ditriflate using carbon monoxide (CO) gas. 19) Proving the utility of this pioneering work, many other researchers have used this method to obtain various derivatives. [20][21][22][23] While this method gives dicarboxylates in good yield under relatively mild, weakly basic conditions, use of the highly to...