Access to indoles via Diels-Alder reactions of 3-vinylpyrroles

(Chemical Equation Presented) N-p-Toluenesulfonyl-3-vinylpyrrole underwent endo-addition [4 + 2] cycloaddition reactions with maleimides and benzoquinones, followed by isomerization to give tetrahydroindoles in good yields. Dehydrogenation with activated MnO₂ in refluxing toluene gave the corresponding indoles in fair to good yields. Detosylation via saponification or with magnesium in refluxing methanol gave the N-H indoles in moderate to good yields. This method for formation of indoles is both convergent and versatile and uses starting materials that are conveniently prepared.