Metal-Catalyzed Cyclizations to Pyran and Oxazine Derivatives

Pyrans are privileged heterocyclic structures found in numerous natural compounds with extraordinary biological activities. The synthesis of these relevant structures has attracted a great deal of attention over the years. Catalytic methodologies based on the activation of neutral unsaturated functionalities of acyclic compounds that undergo intramolecular cyclizations have achieved prominent synthetic relevance. In this short review, we discuss the successful construction of dihydropyran and dihydro-1,4-oxazine derivatives from acyclic precursors by metal-catalyzed intramolecular cyclizations through carbon-carbon, carbon-oxygen, and carbon-nitrogen bond formation. Remarkable synthetic applications are highlighted. 1 Introduction 2 3,4-Dihydropyrans 3 3,4-Dihydro- 1,4-oxazines 4 3,6-Dihydropyrans 5 Synthetic Applications 6 Summary