Abstract
The conformational interconversion among ±sc and ap forms of 9-(2-methylbenzyl)triptycenes is found to occur by two consecutive gear motions: methyl-inside conformers formed by the synchronous rotation about the CH2–Ar and CH2–C9 bonds of the methyl-outside conformers are so unstable that another synchronous rotation takes place in succession to afford methyl-outside conformers. The change in 1H-nmr line shapes and the barriers to rotation are discussed.

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