Trifluoroacetic acid → 1-[4-(3-Pyrrolidin-1-ylmethyl-cyclobutyl)-benzyl]-pyrrolidine

Alternatively, to a stirring solution of 3-pyrrolidin-1-ylmethyl-1-(4-pyrrolidin-1-ylmethyl-phenyl)-cyclobutanol (Example 8, General procedure B, Step D) (1.1 g, 3.5 mmol) in TFA (5.4 mL, 70.1 mmol) was added triethyl silane (5.6 mL, 35.0 mmol). The reaction was then heated to 75 □C (oil bath) for 14 hours. The reaction was then cooled to rt and concentrated under reduced pressure. The residual was taken up in CH2Cl2 and washed with NaHCO3. The aqueous layer was back extracted with 3:1 (CH3Cl:isopropanol). The combined organic layers were dried over MgSO4, filtered though a fritted funnel and concentrated under reduced pressure. Purification of this material was accomplished by flash column chromatography using a 40 M Biotage column, eluting with a gradient of 10%–20% MeOH/CH2Cl2 with 0.3% NH4OH. The product containing fractions were collected and concentrated to give the title compound (324 mg, 18%) as the bis-TFA salt. To this material in EtOAc was added a solution of HCl (2 eq, 2M THF). The resulting solution was stirred over night, and then filtered through a fritted funnel. The solid was collected and dried under reduced pressure to yield the title compound as the bis-HCl salt and as a mixture of isomers.