New, concise route to indoles bearing oxygen or sulfur substituent at the 4-position. Synthesis of (±)- and (S)-(-)-pindolol and (±)-chuangxinmycin

Article abstract of DOI:10.1248/cpb.42.271

A new method for the synthesis of 4-alkoxy- and 4-[alkyl (or aryl)thio]indoles has been developed by using the indolone 3 as a common intermediate. The indolone 3 was prepared from N-(phenylsulfonyl)pyrrole (7) and the α-chlorosulfide 8 in four steps. Heating of a mixture of 3 and an appropriate alcohol in the presence of p-toluenesulfonic acid and cupric chloride afforded the 4-alkoxyindoles 11a-d. The method was applied to the synthesis of (±)-pindolol (19) and (S)-(-)-pindolol (20). Thiols also reacted with 3 in the presence of boron trifluoride to give 4-[aryl (or alkyl)thio]indoles 12, 21a, b, and 22a-d. The (indol-4-ylthio)acetate 22c was employed as a key intermediate for a concise total synthesis of (±)- chuangxinmycin (27).

Full text of DOI:10.1248/cpb.42.271

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