Next, we applied the above optimized conditions to five model heterocyclic compounds 1{1-5} covering a variety of chemotypes (quinoline, pyrimidine, quinoxaline, pyridine, and benzothiazole) and functional groups (Cl, Br, CN), as well as ten cycloalkane-derived trifluoroborates 2{1-10} / carboxylic acids 3{1-10} (C4 to C7) for the parallel synthesis of compound library 4{1-5,1-10} (Scheme 2). [a] Yield of 4{1,5} by LC-MS Isolated yield is given in parentheses Since analysis of the isolated yields for library 4 can be complicated by product losses after HPLC due to their volatility, we mainly rely on the LC-MS-based yields in the following discussion (Figure ). It was found that the average yields of the library members (as detected by LC-MS) were somewhat lower for trifluoroborates 2{1-10} (48%) than for carboxylic acids 3{1-10} (60%). The yield distribution range was narrower for reagents 3{1-10}, which can be considered as an indicator of better method reproducibility under the parallel synthesis conditions. On the other hand, the optimized protocol involved the use of three-fold excess of carboxylic acids 3{1-10}, which in some cases resulted in the formation of double alkylation products -up to 36% for 4{3,9} as detected by LC-MS.