The Mitomycin Antibiotics. Synthetic Studies. IX.¹ A Versatile New Method of Indole Synthesis

Indoles via Dehydrogenation of Pyrroles

“…Remers and Weiss reported a versatile indole synthesis via 4-keto-4,5,6,7-tetrahydroindoles (Scheme 1, equations 1 and 2) [1][2][3], which were prepared by an early method involving 1,3-cyclohexanediones, α-haloketones, and ammonia or primary amines (the Stetter synthesis) [4]. Thus, following elaboration of the ketotetrahydroindole, dehydrogenation was accomplished with Pd/C or DDQ.…”

Methods for Total Synthesis of Steroids. XVIII.1 Δ14 -16-Keto Steroid Approach to Ring D. H.2 Introduction of 17-Carboxy Group. Synthesis of 14α,17β and 14β,17α Isomers of rac-Estra-5(10),6,8-triene-17-carboxylic Acid

“…Methyl /tic-16-Keto-l,3,5(10),6,8,14-Estrahexaene-17-carboxylate (3) . A mixture of 0.5 g of rac-l,3,5(10),6,8,14-estrahexaene-16-one (l,mp 148-149°, ™,013 5.92,6.00 (double peak due to this conjugated CO system), 6.24 µ (conjugated C=C)),lb 10 ml of dimethyl carbonate, 0.25 g of sodium hydride (or an equivalent amount of the 48-55% dispersion in mineral oil), and 2 drops of methanol was refluxed for 5 hr under nitrogen with stirring, then was cooled, cautiously treated with cold methanol to decompose excess sodium hydride, and finally acidified with cold, dilute hydrochloric acid.…”

New Approach for the General Synthesis of Oxotetrahydroindoles via Intramolecular Cycloadditions of Azomethine Ylides with Tethered Alkynes

“…The use of 4-oxo-4,5,6,7-tetrahydroindoles as intermediates for the syntheses of 4-substituted indoles has been well established . One existing literature method consists of a sequence from cyclohexanedione enamines derived from amino acids based on the work of Franck and represents a promising lead into substituted indoles that has yet to be fully exploited.…”