Acyl Azides: Versatile Compounds in the Synthesis of Various Heterocycles­

Abstract

Carbon–nitrogen bond formation is one of the most important reactions in organic chemistry. Various synthetic strategies for the generation of C–N bonds are described in the literature. For example, primary amines can be easily synthesized by the thermal decomposition of an acyl azide to an isocyanate, i.e. the Curtis rearrangement, followed by hydrolysis; the Curtius rearrangement has been used extensively. Furthermore, the advantage of the Curtius rearrangement is the isolation of acyl azides as well as the corresponding isocyanates. The isocyanates can be converted into various nitrogen-containing compounds upon reaction with various nucleophiles that can be used as important synthons for cyclization, in other words, for the synthesis of heterocycles. Therefore, this review demonstrates the importance of acyl azides not only in the synthesis acyclic systems, but also in the synthesis of various nitrogen-containing heterocycles.1 Introduction2 Synthesis of Acyl Azides2.1 Acyl Azides from Carboxylic Acid Derivatives2.2 Acyl Azides by Direct Transformation of Carboxylic Acids2.3 Acyl Azides from Aldehydes2.4 Carbamoyl Azides from Haloarenes, Sodium Azide, and N-Formylsaccharin3 Mechanism of Formation of Isocyanates4 Synthesis of Diacyl Azides5 Synthetic Applications5.1 Synthesis of Pyrimidinone Derivatives5.2 Dihydropyrimidinone and Isoquinolinone Derivatives5.3 Synthesis of Tetrahydroisoquinoline Skeleton5.4 Synthesis of Five-Membered Heterocycles5.5 Heterocycles Synthesized Starting from Homophthalic acid5.6 Heterocycles Synthesized from 2-(Ethoxycarbonyl)nicotinic Acid5.7 Formation of Aza-spiro Compounds5.8 Parham-Type Cyclization5.9 Diazepinone Derivatives5.10 Synthesis of Pyridine Derivatives5.11 Synthesis of Indole Derivatives6 Miscellaneous7 Conclusion