Issue 12, 2007

Joining the rings: the preparation of 2- and 3-indenyl-triptycenes, and curious related processes

Abstract

The indenyltriptycenes, 1 and 2, where the 3- or 2-indenyl, respectively, is attached at the 9-position of the triptycene, are attractive prototypes of molecular gearing systems that can also incorporate a brake. These molecules have been prepared from their respective indenylanthracenes, 3 and 4, by the [4 + 2] cycloaddition of benzyne to the anthracene fragment, and the rotational barriers about the indenyl–triptycenyl single bonds in 1 (12 kcal mol−1) and 2 (<9 kcal mol−1) have been measured. The precursor anthracenes, 3 and 4, were prepared by using palladium-catalysed coupling reactions. Unexpectedly, the Heck-type reaction of 9-bromoanthracene, 5, with indene leads to the formation of 3-indenylanthracene 3; moreover, this process is accompanied by a novel palladium-catalysed carbocyclisation reaction leading to the indenophenanthrylene 9. The addition of benzyne to 9-(3-indenyl)anthracene, 3, yields the corresponding indenyltriptycene, 1, and, surprisingly, the anthracenyl methano-bridged phenanthrene 16. It has been demonstrated that 2-arylindenes can act as 1,3-dienes in the [4 + 2] cycloadditions of benzyne. The products 2, 7a, 9 and 16 have been characterised by X-ray crystallography.

Graphical abstract: Joining the rings: the preparation of 2- and 3-indenyl-triptycenes, and curious related processes

Supplementary files

Article information

Article type
Paper
Submitted
09 Mar 2007
Accepted
03 May 2007
First published
17 May 2007

Org. Biomol. Chem., 2007,5, 1952-1960

Joining the rings: the preparation of 2- and 3-indenyl-triptycenes, and curious related processes

K. Nikitin, H. Müller-Bunz, Y. Ortin and M. J. McGlinchey, Org. Biomol. Chem., 2007, 5, 1952 DOI: 10.1039/B703437G

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