Cycloaminals Of Trichloroacetaldehyde: Synthesis And Their Use As Carbene-Precursors

Trichloroacetaldehyde was successfully used for the cyclisation of bis-amidines of oxalic acid 1 to afford cycloaminals in good yields. Although prototropism is a characteristic feature of the amidines the cyclisation reaction can be realized in a regioselective manner to give three types of cycloaminals 6, 7 and 8. Starting from cycloaminals 8 carbenes can be generated which immediately dimerize to the corresponding 2,3,6,7-tetrakis(arylamino)-1,4,5,8-tetraazafulvalenes 5.