Double-twist Möbius aromaticity in a 4n+ 2 electron electrocyclic reaction.

One transition state for the 10 electron (4n+ 2) electrocyclisation of Z,E,Z-decapentaene is predicted to have the properties of a double-twist Möbius strip, with delocalised bond lengths and the NICS(0) magnetic index typical of aromaticity; a 5,6-di-(t)Bu substituted decapentaene is predicted to react in this mode in preference to the competitive six-electron electrocyclisation.