We thus sought to identify mild conditions that would support the Friedländer reaction of model β-keto amide 5 (Fig. , Supplementary Fig. ), and apply these conditions to peptides generated using IVT. We examined the reaction of 5 with 2-aminoacetophenone 6 to generate quinoline 15 in acetic acid and acetic acid/water mixtures at temperatures between RT and 60 °C. Reactions were performed using 330 mM of 5 and 6 and the formation of quinoline 15 was monitored as a function of time using LC-MS (Fig. ). We found that all conditions tested supported the Friedländer reaction of β-keto amide 5 to generate the expected quinoline product 15. Conversion was most rapid at 60 °C in AcOH or H 2 O/AcOH mixtures or at 40 °C in AcOH (Fig. ). To evaluate reaction scope under these conditions, we treated β-keto amide 5 with a collection of nine structurally diverse 2-aminoarylcarbonyl substrates 6-14 (Fig. and Supplementary Fig. ). Substrates 6 and 9-13 reacted cleanly with β-keto amide 5 with full conversion to the expected quinoline products 15 and 18-22 after 48 h at 60 °C in AcOH. Reactions with 2-aminobenzaldehydes 7 and 8, which polymerize under acidic conditions , and kynurenine 14, led to lower levels of product formation (Supplementary Fig. ). Quinolines 15-20 were synthesized on a preparative scale and the products were characterized using LC-HRMS and NMR.