J. Bornstein

Structural effects on the isoindole-isoindolenine equilibrium. Substitution in the pyrryl ring

Abstract The influence of substitution in the pyrryl ring on the isoindole-isoindolenine equilibrium has been studied by NMR spectroscopy. Electron-releasing groups selectively stabilize the isoindolenine tautomer in which the substituent is conjugated with the π-system, while electron-withdrawing groups have the opposite effect. However, sequential introduction of identical groups into the 1- and 3-positions leads, first to a shift of the equilibrium in one direction, then to a shift in opposite direction. Reasons for this behavior are discussed.

Synthesis of isoindole by retro-Diels–Alder reaction

Thermal fragmentation of 1,2,3,4-tetrahydro-1,4-epiminonaphthalene at reduced pressure affords pure isoindole in essentially quantitative yield.

Benz[e]isoindole

Further experimental confirmation of the validity of prediction based on HMO calculations of the stability of isoindoles is provided by the synthesis of benz[e]isoindole, the second and simplest example to date of an isolable isoindole which is free of substituents in the pyrrole ring.

Synthesis, isolation, and characterization of naphtho[2,3-c]thiophen

1,3-Dihydronaphtho[2,3-c]thiophen 2-oxide (1) undergoes dehydration when subjected to flash vacuum thermolysis to afford the heretofore elusive naphtho[2,3-c]thiophen (2) as a highly reactive yellow solid.