The Synthesis of 5-Keto-1,3,4,5-tetrahydrobenz[cd]indole. A Synthesis of 4-Substituted Indoles

Abstract

The Synthesis of 5-Keto-l,3,4,5-tetrahydrobenz[cd]indole. A Synthesis of 4-Substituted Indoles By Frederick C. Uhle

Recent Studies in the Field of Indole Compounds

“…The ring structure of this cyclization product was proved by deacetylation and reduction of (V) with hydrazine [108J under mild conditions, followed by thermal decarboxylation of the resulting acid (VIII) to 1,3,4, 5-tetrahydrobenz[cdJindole (X) [195,17,196]. This compound (X) was identical with an authentic sample kindly sent to us by F. C. UHLE, of Harvard University.…”

Total synthesis of dihydrolysergic acid and dihydrolysergol: development of a divergent synthetic strategy applicable to rapid assembly of D-ring analogs

“…Notably, the latter natural product has only been prepared by semisynthesis from lysergic acid and the work herein discloses the first total synthesis of this natural product by an alternate route. The first of these reactions is a powerful intramolecular Larock indole cyclization 10,11 for formation of an embedded tricyclic indole isomeric with Uhle’s 12 and Kornfeld’s 6a ketones widely used in accessing the ergot alkaloids (Figure 2). The second of the reactions is a powerful inverse electron demand Diels–Alder reaction of 5-carbomethoxy-1,2,3-triazine with a conjugated enamine for the regiospecific introduction of a functionalized pyridine, 13 serving as the precursor for a subsequent and remarkably diastereoselective reduction to the N -methylpiperidine D-ring.…”

A Pd(0)-Mediated Indole (Macro)cyclization Reaction

“…19 For example, tricyclic indole 34 serves as a synthetic precursor to Uhle’s 20 and Kornfeld’s 21 ketones that have been extensively utilized in the synthesis of ergot alkaloids including lysergic acid and its derivatives, complementing its use in the syntheses of macrocyclic indoles such as chloropeptin II, 5 kapakahines, 22 and potentially stephanotic acid. 1l–t …”