To a solution of the isoquinolinone (1.156 g, 9.90 mmol) and tert-butyl alcohol
(0.88 mL, 11.9 mmol) in THF (30 mL) at −78 °C was added liquid ammonia (about
280 mL). Lithium was added in small pieces until the blue coloration persisted, after
which the solution was stirred at −78 °C for 30 min. The blue coloration was dissipated
with piperlyne, 4-methoxybenzyl chloride (4.83 g, 31.00 mmol) in THF (5 mL)
was introduced by syringe, and the mixture was stirred for an additional 150 min at
−78 °C. Solid ammonium chloride was added and then the ammonia was allowed to
evaporate. The pale yellow residue was partitioned between CH2Cl2 (30 mL) and
water (40 mL). The layers were separated, and the aqueous layer was extracted
with CH2Cl2 (2 × 30 mL). The combined organic layers were washed with 10%
sodium thiosulfate solution (20 mL), dried over magnesium sulfate, and concentrated.
Flash chromatography (EtOAc:hexane, 2:1) on silica gave 2.21 g (75%) of the
tetrahydroisoquinolinone.
Reference: Schultz, A. G.; Guzi, T. J.; Larsson, E.; Rahm, R.; Thakker, K.
Bidlack, J. M. J. Org. Chem. 1998, 63, 7795–7804.
