Novel synthesis of cyclobutanone derivatives via dimetalation of iminium ions with the TiCl4–trialkylamine reagent systemElectronic supplementary information (ESI) available: 13C NMR spectra of compounds 1a, 2a, 3a, 4a, 5a, 6a, 7a and 7b. See http://www.rsc.org/suppdata/cc/b1/b103112k/
Abstract