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Has been widely used in the Leimgruber-Batcho indole synthesis by the reductive cyclization of pyrrolidine ortho-nitro enamines; see N,N-Dimethylformamide dimethyl acetal, A15350.• A convenient procedure for the conversion of carbonyl compounds to their pyrrolidine enamines involves reaction with pyrrolidine, either neat or in ethereal solution, in the presence of magnesium sulfate: Org. Prep. Proced. Int., 8, 211 (1976).