Scheme 2.

Synthesis of the required A/B units. Footnote for Scheme 2. Y = Me (Ref. ⁸): Y = H; 3-F; 2-F, 3-OMe; 2,3-diOMe (Ref. ¹⁰): 3-aza, 2-OMe; 3-aza, 4,5-diOMe; 4-aza, 2,3-diOMe (Ref ¹¹); Y = 2,3-O(CH₂)₂O– (route 2, yield 52%); 4-aza, 3,5-diOEt (route 2, yield 56%); 4-aza, 3-OMe, 5-OEt (route 2, yield 68%); 4-aza, 3-OMe, 5-OiPr (route 2, yield 78%) 4-aza, 3-OMe, 5-OnPr (route 2, yield 75%), 4-aza, 3-OEt, 5-OnPr (route 2, yield 78%) (this paper). (i) LiTMP, then AcOH; (ii) Et₃SiH, TFA, DCM, 20 °C; (iii) Cs₂CO₃, Pd(PPh₃)₄, PhMe/DMF, 110 °C (sealed tube), 5 h.