A new method for the synthesis of 5,9‐diaza[5]helicenes is presented using 2,3‐bis(acylamino)‐substituted ortho‐terphenyls as precursors. Activation of the amide groups and electrophilic substitution at the ortho positions of the adjacent phenyl groups leads to the 5,9‐diaza[5]helicenes. A stepwise reaction including protection of the first amino group, amide formation at the second amino group with subsequent cyclization, followed by deprotection, amide formation and cyclization at the first amino group ensures that both electrophilic substitutions take place at sufficiently activated arenes and allows for the different substituents at the diaza[5]helicenes brought in with the amide groups. The terphenyl precursors are synthesized by two Suzuki couplings of suitably substituted building blocks. Three different 5,9‐diaza[5]helicenes with aliphatic, alkenyl and methoxycarbonylalkyl substituents were prepared; the latter would allow to attach further functionalities by ester or amide linkage.

Double ortho-fusion in suitably substituted ortho-terphenyls are used for the synthesis of diaza[5]helicenes. Bis(carboxamido)-substituted ortho-terphenyls can be condensed to 5,9- and 6,9-diaza[5]helicenes, where substituents at the 5,9- and 6,9-positions, respectively, are introduced with the carboxamido groups. While a twofold coupling sequence with intermediate protection of one amino group has to be used for 5,9-diaza[5]helicenes, a more concise sequence avoiding the protection leads to 6,9-diaza[5]helicenes. The simple heating of ortho,ortho’-diazido-terphenyls furnishes 5,8-dihydroindolo[2,3-c]carbazoles, i.e., [5]helicenes with alternating benzene and pyrrol rings.

The total synthesis of decarboxyaltenusin (5’-methoxy-6-methyl-[1,1’-biphenyl]-3,3’,4-triol), a toxin produced by various mold fungi, has been achieved in seven steps in a yield of 31% starting from 4-methylcatechol and 1-bromo-3,5-dimethoxybenzene, where the longest linear sequence consists of five steps. The key reaction was a palladium-catalyzed Suzuki coupling of an aromatic boronate with a brominated resorcin derivative.

Aryl-substituted biguanides are rubber vulcanization accelerators of moderate activity. The relation between the chemical constitution of the substituted radicals and the activity of the biguanides is, in general, about the same as found by other investigators for other types of accelerators. α-o-Tolylbiguanide has a fairly great activity in certain commercial rubber stocks.

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