Carbamoylcobalt(III) salophen compounds, such as 4, are sources of carbamoyl radicals under either thermal or photolytic conditions. Generation of N,N-dimethylcarbamoyl radicals, e.g.5, in the presence of trapping agents such as diphenyl disulfide or 2,2,6,6-tetramethylpiperidin-1-yloxy radical 7 afforded the expected amido derivatives, e.g.6 and 8, respectively. These radicals 5 also underwent oxidative intermolecular addition to styrene; the thermal process gave the E-cinnamide 10 exclusively, whereas under photochemical conditions a 1:1 mixture of E- and Z-cinnamides, 10 and 11, respectively, was obtained. A series of N-alkenyl-N-alkylcarbamoylcobalt(III) salophens have also been prepared (i.e.14, 33 and 43), and are shown to be suitable precursors for the synthesis of β-,γ- and δ-lactams through the 4-, 5- or 6-exo-trig-modes of cyclisation of the corresponding intermediate carbamoyl radicals. The products of these cyclisations, N-alkyl-3-lactamidomethyl radical (i.e.16, 34 or 46) are trapped by the cobalt(II) salophen to give the corresponding alkylcobalt(III) salophens (e.g.16→17). Although these alkylcobalt salophens appeared to be stable at temperatures ⩽40 °C, under the thermolytic conditions for radical generation that were usually employed (110 °C) dehydrocobaltation occurred, and the unsaturated lactam was formed. Results concerning the introduction of side-chain oxygen functionality at the product radical centre in tandem with the carbamoyl radical cyclisation are also presented. Computer-generated molecular modelling calculations supporting the novel 4-exo-trig-cyclisation of 15 are discussed.