Synthesis of Quinoxalines from Heterocyclic Systems

Synthesis of Quinoxalines from Heterocyclic Systems 2.6.2.2 From Azirines... 

Chapter 2 covers recent advances in the Synthesis of Quinoxalines involving the methods based on the (a) condensation of 1,2-diaminobenzenes and derivatives with various two-carbon unit suppliers, (b) condensation of o-benzoquinone diimines and diimides with various two-carbon unit suppliers, (c) condensation of A,A-dimethyl(dibenzyl)ethylenediamine with 1,2- and 1,4-dihydroxybenzenes, (d) synthesis of quinoxalines from aniline and its derivatives, (e) synthesis of quinoxalines from heterocyclic systems and (f) synthesis of quinoxalines based on the carbocyclic system. 

Synthesis of Quinoxalines from Various Heterocyclic Systems, Containing Neither a Pyrazine ring nor a Benzofragment... 

Pyrrolo[2,3-b]quinoxalines have also been named as 4,7-diaza-5,6-benzindoles. Until recently derivatives of this ring system were obtained by synthesis of the pyrazine ring. Recently methods have been described starting from suitably substituted quinoxalines. The first reported synthesis of this heterocycle gave the diphenyl compound 124 and its 2-p-tolyl... 

Miscellaneous Reactions. Palladium dba has been employed as a catalyst for effecting various annulation reactions. Mediumsized nitrogen heterocycles have been prepared from allenes and amino alkenyl hahdes in the presence of a Pd(dba)2/PPh3 catalyst system. 1,3-Dienes can be converted to benzofuran derivatives upon reaction with o-iodoacetoxy arenes and this reaction has been applied in the synthesis of new coumarins. Dihydro-quinoxalines and quinoxalinones have been obtained via reductive annulation of nitro enamines (eq 26). ... 

All known methods for the synthesis of the pyrrolo[l,2-a]quinoxaline system can be divided into three groups. The first group of methods is based on derivatives of quinoxaline, the second group contains methods based on pyrroles, and the third group contains other methods including the recycUzation of other heterocycles and also syntheses from nonheterocycUc systems. This chapter examines methods of synthesis based on derivatives of quinoxaline and the methods of the third group. Possible variants of the construction of the pyrrolo[l,2-a]quinoxaline system based on quinoxalines are presented below. 

As distinct from imidazo[l,2-a]quinoxaline derivatives for which the method of construction of the heterocycle through the formation of the C(3a)-C(4) bond is basic (see Sect. 4.5.1), there are only two publications describing the Ali-type synthesis of representatives of the tricyclic imidazo[l,5-a]quinoxaline system (Malamas et al. 

---