One-pot conversion of tetraiminodiphenols to diiminodiaminodiphenols via methyl transfer at aluminium

The [2+2] macrocyclic Schiff base {[2-(OH)-5-(tBu)C6H2-1,3-CH][(CH2CH2)(2-C6H4N)2]}2 (1) is readily converted to the diiminodiamine {[2-(OH)-5-(tBu)C6H2-1-(CH)-3-C(Me)H][(CH2CH2)(2-(N)-2′-C6H4NH)2]}2 (2) via methyl group transfer from Me3Al (four equivalents) and subsequent hydrolysis. When compound 1 is reacted with two equivalents of Me3Al, the dinuclear complex {(Me2Al)[2-(O)-5-(tBu)C6H2-1,3-(CH)2][(CH2CH2)(2-C6H4)2N)2]}2 (3) is formed. The structures of the macrocycles 1 and 2 are described (in the case of 1, the toluene solvate has also been structurally characterised).