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The syntheses and photochemical properties of the novel aminoaryldiarylboranes, 4, which are isoelectronic with triarylmethane dyes, and also pyrrolyl-8, and indolyl-diarylboranes 11, are described. The fluorescence spectra are strongly dependent on the solvent. The use of o-disubstituted arenes as stabilizing substituents at the boron atom leads to highly coloured solids which are stable to air and moisture. The structures of the triarylboranes 4a and b were confirmed by X-ray analyses.

Modern transition-metal-catalyzed cross-coupling reactions, especially of the Kumada, Heck, and Suzuki types, have provided facile access to various bridge-annelated [2.2]paracyclophane derivatives including trifoliaphane and its tribenzo analog. The reduction of trifoliaphane with potassium metal in [D8]-THF led to hexakis[p-benzyl]benzene anion, which could efficiently be trapped with various electrophiles. Highly efficient multifold Suzuki couplings were performed with hexabromobenzene, octabromonaphthalene, and hexabromotriphenylene. The obtained hexa- and octaalkenylarene derivatives disclose interesting molecular shapes. Eventually, a newly developed cascade coupling of bromoarenes containing peri-positioned C-H bonds has led to indeno-annelated polycyclic aromatic hydrocarbons including indenocorannulene as well as the tetrakis- and tris(tert-butylindeno)pyrene which disclose very interesting spectroscopic properties. In particular, tetrakis(tert-butylindeno)pyrene self-assembles in solution by way of π-stacking, and it can be reduced with potassium metal to a stable dianion, a readily dimerizing trianion radical, and a tetraanion.

The 1,3-bis(4-acylphenyl)propanes 2, 3, 9, 12, and 15 were subjected to a cyclization by reductive coupling with low-valent titanium ( These preparations require many synthetic steps and the total yields are usually low. Hence, a convenient and efficient synthesis of [3.2]cyclophanes is of particular interest.In the course of our studies of "twinned" cyclophanes') a synthesis producing [3.2]paracyclophane-IO-enes in high yields was needed, and it appeared that the titanium-induced reductive coupling of appropriate diketones -the McMurry reaction6) -could be a suitable method. It is well known') that the McMurry reaction is one of the best possibilities to synthesize sterically hindered alkenes. Furthermore, highly strained cyclic compounds were prepared by this method" also, but so far only the formation of additional bridges in cyclophanesga) and the syntheses of macro- SynthesisIn effect, the starting material for the synthesis of [3.2]-paracyclophane-10-enes by the titanium-induced reductive coupling is the easily available 1,3-diphenylpropane lo) (1). The twofold and regioselective Friedel-Crafts acylation of 1 with acetyl chloride and propionyl chloride under optimized reaction conditions gave satisfactory yields of the corresponding 1,3-bis(4-acylphenyl)propane 2 and 3 lo), respectively. The reversible acylation reaction strongly prefers a substitution at the para position of each of the phenyl groups, and no contamination with the sterically hindered Chem.