Conjugate Addition Routes to 2‐Alkyl‐2,3‐dihydroquinolin‐4(1H)‐ones and 2‐Alkyl‐4‐hydroxy‐1,2‐dihydroquinoline‐3‐carboxylates

Under CuBr·SMe2/PPh3 catalysis (5/10 mol‐%) RMgCl (R = Me, Et, nPr, CH=CH2, nBu, iBu, nC5H11, cC6H11, Bn, CH2Bn, nC11H23) readily (–78 °C) undergo 1,4‐addition to Cbz or Boc protected quinolin‐4(1H)‐ones to provide 2‐alkyl‐2,3‐dihydroquinolin‐4(1H)‐ones (14 examples, 54–99 % yield). Asymmetric versions require AlEt3 to Boc‐protected ethyl 6‐substituted 4(1H)‐quinolone‐3‐carboxylates (6‐R group = all halogens, n/i/t‐alkyls, CF3) and provide 61–91 % yield, 30–86 % ee; any halogen, Me, or CF3 provide the highest stereoselectivities (76–86 % ee). Additions of AlMe3 or Al(nC8H17)3 provide ≈ 45 and ≈ 75 % ee on addition to the parent (6‐R = H). Ligand (S)‐(BINOL)P–N(CHPh2)(cC6H11) provides the highest ee values engendering addition to the Si face of the 4(1H)‐quinolone‐3‐carboxylate. Allylation and deprotection of a representative 1,4‐addition product example confirm the facial selectivity (X‐ray crystallography). Directing ester functions (R = CO2Et) “give a big hand” to copper catalysed 1,4‐additions of organometallics to medicinally relevant quinolin‐4(1H)‐ones. In the absence of any directing group only 11 % ee is realised for the addition of EtMgBr. In the presence of the CO2Et activating group, AlEt3 may be added in up to 82 % ee providing 6‐halo building block starting materials for quinolone species.