Convenient one-pot synthesis and coordination chemistry of a bulky asymmetrical 9,10-dihydroacridine-based ligand

An asymmetrical, 9,10-dihydroacridine-based proligand, H[NNO^tBu], featuring a diphenylamine and a tert-butyl ether substituent on the 4 and 5 positions is reported. The ligand can be synthesized in a one-pot, palladium-catalysed reaction in reasonable yields from symmetrical starting materials. The coordination chemistry of this ligand has been investigated towards a range of main group metals. The reaction between the proligand H[NNO^tBu] and benzyl potassium proceeded as expected, leading to deprotonation of the amine to give the potassium amide in good yields. In contrast, the reactions between H[NNO^tBu] and MeMgBr or AlMe₃ were found to be more complex, leading to both deprotonation of the amine and C−O bond cleavage of the ligand's tert-butyl ether group. This C−O bond cleavage was found to be preventable when using the bulkier reagent n-butyl-sec-butylmagnesium, yielding the monometallic complex [NNO^tBu]Mg^sBu in good yields.