Asymmetric Michael Addition of Dimethyl Malonate to 2 Cyclopenten-1-one Catalyzed by a Heterobimetallic Complex

Abstract

A. Preparation of GaNa-(S)-BINOL((S)-2) Solution (0.05 M).2 A flame-dried 1L, three-necked round-bottomed flask with 24/40 joints and a 1.5" Teflon coated egg-shaped magnetic stir bar is brought into a nitrogen filled glovebox (Note 2). The flask is charged with gallium (III) chloride (5.0 g, 28.4 mmol, 1.0 equiv) (Notes 3 and 4). The flask is sealed with three rubber septa (one of which is fitted with an internal temperature probe) brought out of the glovebox, and put under positive pressure of nitrogen via a needle attached to a nitrogen line. Another flame-dried 1L, three-necked round-bottomed flask with 24/40 joints and a 1.5" Teflon coated egg-shaped magnetic stir bar is charged with (S)-(-)-1,1'-bi(2-naphthol) ((S)-BINOL, (S)-1) (16.26 g, 56.8 mmol, 2.0 equiv) (Note 5). The flask is sealed with three rubber septa (one of which is fitted with a thermometer) and evacuated and backfilled with nitrogen three times (5 minutes under vacuum per cycle). A flame-dried 500 mL round-bottomed flask with a 24/40 joint and a 1" Teflon coated egg-shaped magnetic stir bar is charged with sodium tert -butoxide (10.92 g, 113.6 mmol, 4.0 equiv) (Note 6). The flask is sealed with a rubber septum and evacuated and backfilled with nitrogen three times (5 minutes under vacuum per cycle).