Abstract
cis,cis-1,5-Cyclooctadiene is the starting point for the synthesis of quinoxalineand pyrazinecontaining heterocycles with three, four or five rings in linear arrays with a central eightmembered carbocyclic ring.
Highlights
Introduction cis,cis-1,5-Cyclooctadiene is a commercially available and inexpensive starting material
Our interest in the synthesis of heterocycles, and pyrazines and quinoxalines in particular, led us to speculate that this eight-membered ring bis-alkene could be made the starting point for the construction of diverse novel heterocycles, but avoiding any transannular processes which would remove the eight-membered feature
6,7,8,9,10,11-Hexahydrocyclocta[b]quinoxaline 10 is produced more either by the reaction of cyclooctane-1,2-dione (‘suberil’) with ortho-phenylenediamine, though minimal details were given in the publication describing this route,[8] or most of all, as recently reported, by the reaction of cyclooctanone with ortho-phenylenediamine in the presence of KOH and air in PEG-400 at 60 °C.9
Summary
Mostafa Honari Alamdari,a,c Madeleine Helliwell,b Mehdi M. Introduction cis,cis-1,5-Cyclooctadiene is a commercially available and inexpensive starting material. It has been utilised previously in several significant ways, for example as the starting material for the synthesis of 9-borabicyclo[3.3.1]nonane (9-BBN) the important hydroborating reagent, as a ligand (COD) for metal centres, for conversion into 1,3,5-cyclooctatriene (COT) a widely used ligand, and for the study of transannular interactions involving the two alkene units. Our interest in the synthesis of heterocycles, and pyrazines and quinoxalines in particular, led us to speculate that this eight-membered ring bis-alkene could be made the starting point for the construction of diverse novel heterocycles, but avoiding any transannular processes which would remove the eight-membered feature. Strong heating (Bunsen burner; open vessel) of the sulfone 6 produced a low yield of the tetraphenyl-substituted cycloocta[1,2-b:5,6-b']diquinoxaline 7 (Scheme 3).[4]
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