3‐Lithiopyrroles by Halogen‐Metal Interchange of 3‐Bromo‐1‐(triissopropylsilyl)pyrroles. Synthesis of Verucarin E and Other 3‐Substituted Pyrroles. Preliminary Communication

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Abstract
3‐Lithio‐1‐(trimethylsilyl)pyrrole (7, Schem 2), obtained by halogen‐metal interchange from the 3‐bromo compound 2, reacted with various electrophilic reagents to provide products, which on fluoride ion desilylation, gave 3‐substituted pyrroles in good overall yields. One such pyrrole 13 (Schem 3), was converted into 2‐formyl‐3‐octadeclpyrrole (14), reputed to be a metabolite of the marine sponge Oscarella lobularis.3,4‐Dibromo‐1‐(triisopropylsityl)pyrrole (5) was efficiently transformed, by a process involving two consecutive bromine‐lithium exchange reactions (Scheme 4), into the antibiotic verrucarin E 17.