Cyclization, Ring-Expansion, and Several Cascade Reactions Utilizing Allenylic Molecular Structure Characteristics

Abstract

Various kinds of new reactions based on allenylic molecular structure characteristics have been described. Specifically, mild alkaline hydrolysis of diethyl α-acetylamino (or methoxy) -α-alkynylmalonates generates conjugated allenyl esters which promote 5-endo-mode heterocyclic cyclization giving trisubsutituted oxazoles, SH-enzyme inhibition, new chiral pyrrolinones (cathepsin B inhibitors) formation, and Myers-type biradical aromatization in a cascade reaction manner. Systematic ortho vicinal-endo-mode-, geminal spiro-endo-mode-, and meta ansa-endo-mode-cyclization reactions have been accomplished by using numerous conjugated allenyl ketones and Lewis acids. Base-mediated and palladium (0) -catalyzed cascade heterocyclic and carbocyclic ring-expansion reactions have been achieved by using hydroxy-substituted allenyl cyclic compounds.