Selective lithiation of 2,3-dibromo-1-methylindole. A synthesis of 2,3-disubstituted indoles

✍ Scribed by Yanbing Liu; Gordon W Gribble

• Book ID: 104251986
• Publisher: Elsevier Science
• Year: 2002
• Tongue: French
• Weight: 103 KB
• Volume: 43
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(02)01710-0

✦ Synopsis

Indole (1) can be converted to 2,3-dibromo-1-methylindole (3) in two operations (92% yield). Treatment of 3 with tert-butyllithium effects clean monolithiation to 3-bromo-2-lithio-1-methylindole (4), which can be trapped with various electrophiles to afford the 3-bromo-2-substituted indoles (5-8) in 85-99% yield. A second bromine-lithium exchange reaction and quenching with electrophiles yields the 2,3-disubstituted indoles (9-10) in 88-95% yield.