Novel ringtransformations of pyrimidines and pyridines by intramolecular inverse electron demand Diels‐Alder reactions

Abstract

Abstract 2‐(1,1‐Dicyanopent‐4‐yn‐1‐yl)pyrimidines ( 1 ) and 2‐(1,1‐dicyanopent‐4‐yn‐1‐yl)nitropyridines ( 4 ) undergo intramolecular inverse electron demand Diels‐Alder cycloaddition across the C 2 ‐C 5 positions; these adducts lose hydrogen cyanide instantaneously, yielding 7,7‐dicyano‐6,7‐dihydro‐5H‐1‐pyrindines ( 3 ) and 1,1‐dicyano‐2,3‐dihydronitroindenes ( 6 ), respectively. The intramolecular cyclo‐additions of the pyridine derivatives represent the first examples of inverse electron demand reactions in pyridines.