Concave reagents, 3. Synthesis, basicity, and conformation of new concave pyridines

Abstract

Abstract Eight new bimacrocyclic concave pyridines 9 and six monomacrocyclic and open‐chain analogues 10 – 12 were synthesized in overall yields up to 40% (up to 75% for nonmacrocyclic pyridines) starting from 2,6‐pyridinedicarbaldehydes 1 , diamines 2 and diacyl dichlorides 7 . Their basicities cover a range of more than three orders of magnitude. They are determined not only by the substitution pattern of the pyridine ring, but also by the overall structure of the whole molecule and by its ability to stabilize the positive charge of a proton intramolecularly. The conformations of the bimacrocyclic bislactams 9 in solution and in the solid state were investigated spectroscopically, the structure of 9b could be determined by X‐ray analysis.