Lithium Hexamethyldisilazide → tert-Butyl 2-(4-((5R,7R)-2-oxo-3-oxa-1-azaspiro[4.4]nonan-7-yl)phenyl)acetate

Participants

Reaction Steps

To a solution of (5R,7R)-7-(4-bromophenyl)-3-oxa-1-azaspiro[4.4]nonan-2-one (Int. 4, 2.1 g, 7.09 mmol) in THF (25.3 ml) at room temperature was added LiHMDS (7.80 ml, 7.80 mmol). The solution was stirred for 15 min. Next, Pd2(dba)3 (0.195 g, 0.213 mmol), 1,2,3,4,5-pentaphenyl-1′-(di-t-butylphosphino)ferrocene (0.151 g, 0.213 mmol), and (2-(tert-butoxy)-2-oxoethyl)zinc(II) bromide, tetrahydrofuran (7.07 g, 21.27 mmol) were sequentially added. The slurry was stirred at 24° C. for 2 h. LCMS analysis showed complete consumption of the starting material. The reaction mixture was diluted with ethyl acetate and washed with 1M HCl. The organic layer was dried over MgSO4, filtered and concentrated. The crude material was purified on a silica gel cartridge (40 g) using hexane: acetone 100:0 to 0:100 over 25 CV. tert-Butyl 2-(4-((5R,7R)-2-oxo-3-oxa-1-azaspiro[4.4]nonan-7-yl)phenyl)acetate (2.35 g, 7.09 mmol) was isolated. HPLC retention time=0.95 min (Condition I): LC/MS M+1=332: 1H NMR (400 MHz, chloroform-d) δ 7.27-7.21 (m, 2H), 7.21-7.15 (m, 2H), 5.11 (br. s., 1H), 4.40-4.26 (m, 2H), 3.53 (s, 2H), 3.22-3.01 (m, 1H), 2.36 (dd, J=13.2, 7.3 Hz, 1H), 2.25-2.10 (m, 2H), 2.04-1.92 (m, 2H), 1.91-1.76 (m, 1H), 1.47 (s, 9H).

Provenance & Evidence