The preparative value of the I-(phenylsulfonyl) N-blocking and directing group for the synthesis of 3-acylpyrroles has been further evaluated. Acetylation and benzoylation are strongly regiospecific and give good yields. However, the regiospecificity is not general and other substitution reactions give mixtures of 2-and 3-substitution or even mostly 2-substitution. Friedel and Crafts rert-butylation gives 3-rerr-butyl-I-(phenylsulfonyl)pyrrole and provides a useful route to rert-butylpyrrole, but ethylation and isopropylation give mixtures. Acylations of 2-and 3-alkyl-I-(phenylsulfonyl)pyrroles show little evidence of useful regiospeeifieity.
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