One‐Pot Preparation of [<i>n</i>]Ladderanes by [2π + 2π] Photocycloaddition

Abstract

Abstract A new method for the preparation of [ n ]ladderanes is presented, based on a one‐pot [2π+2π] photocycloaddition of [2.2]paracyclophane pseudo‐ gem bis(polyene) precursors. [3]‐ and [5]ladderanes could be isolated and were fully characterized, including their X‐ray structure analysis. The overall chemical yields from [2.2]paracyclophane as starting material were found to be 53 % ([3]ladderane) and 38 % ([5]ladderane). Preliminary investigations of their photochromic properties (reversible change from yellow or red to colourless forms) are described. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)