A series of three (E)-2-alkylidene-1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxaline compounds

The three title quinoxaline derivatives, (E)-2-(4-methylbenzylidene)-1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxaline, C₃₀H₂₈N₂O₄S₂, (II), (E)-2-(4-methoxybenzylidene)-1,4-di-ptosyl-1,2,3,4-tetrahydroquinoxaline, C₃₀H₂₈N₂O₅S₂, (III), and (E)-2-(3-chlorobenzylidene)-1,4-di-p-tosyl-1,2,3,4-tetrahydroquinoxaline, C₂₉H₂₅ClN₂O₄S₂, (IV), were synthesized by palladium-catalyzed hetero-annulation. The E configuration of the exocyclic double bond in the three compounds has been established by the present X-ray study. The saturated part of the quinoxaline moiety in all three compounds assumes a distorted chair conformation. The numerical descriptors indicate a high degree of isostructurality between compounds (II) and (III), but no isostructurality with compound (IV).