The construction of the pyrrolidine ring about a nitrogen of a primary amine by a reductive condensation reaction using 2,5-dimethoxytetrahydrofuran and sodium borohydride in acidic water medium is described. The reaction is fast, affords good to excellent yields and appears insensitive to electron effects and severe steric hindrance; it is found to be compatible with a large variety of aryl substituents, including nitro and oxo groups. The reaction allows the introduction of two deuterium atoms, with label conservation, in both the alpha-positions of the pyrrolidine ring by the use of sodium borodeuteride instead of sodium borohydride.
