Reactions of 2-Hydroxytryptophol : Results of Strong Acid and Alkaline Treatments of 2-Hydroxytryptophol

Abstract

Upon being warmed at 90°C in trifluoromethanesulfonic acid for 42-78 h, 2-hydroxytryptophol (4a) gave 3-ethylideneoxidoles (E-and Z-form) (5a), while 3-methyl-(4b) or 3-ethyl-2-hydroxytryptophol (4c) gave the corresponding 3-alkylideneoxindoles (5b, 5c) and 3, 4-dialkylcarbostyrils (6_{1-b, c}, 6_H-c). On tosylation in pyridine, 4a gave spiro-(3)-cyclopropane-(8) and 3-chloroethyl-oxindole (10), and the corresponding tosylate (7a), but 4b and 4c gave only the corresponding tosylates (7b, 7c). The tosylate 7a and the chloroethyl compound 10 reacted in alkaline ethanol to afford the spiro compound 8, whereas the tosylates 7b, 7c gave 2-ethoxy-3-methyl (or ethyl)-3-hydroxyethylindolenines (9b, 9c) under the same conditions.