New potentially chelating chiral magnesium amide bases for use in enantioselective deprotonation reactions

A series of chiral secondary amines, incorporating a 5- or 6-membered heterocycle, were synthesised and used to prepare novel chiral magnesium bisamide reagents. These amide bases were subsequently applied within asymmetric deprotonation reactions to probe the potential for chelation-assisted selectivity enhancement. Good levels of selectivity could be achieved (up to 87:13 e.r. (R:S)) across a range of prochiral cyclohexanone substrates when employing a thiophene-derived magnesium bisamide complex.