h nmr cdcl 3 400 mhz u03b4 2 18 s 3h 3 20 s 3h 3 74 s 3h 4 82 s 2h to a solution of 2 acetoxy n methoxy n methyl acetamide 14 80 6 g 500 mmol in methanol 1000 ml were added while stirring 1 0m sodium methoxide in methanol 5 ml 5 mmol and the pale yellow solution was stirred at rt for 3 h after the addition of 37 hcl 0 45 ml ca 5 mmol the reaction mixture was evaporated to dryness affording 58 8 g 98 7 crude 12 as a pale yellow liquid vacuum distillation over a 10 cm vigreux column afforded 54 5 g 91 6 weinreb amide 12 as a colorless oil bp 59 60 u00b0 c 0 5 mbar 1 h nmr cdcl 3 400 mhz u03b4 3 10 s 1h 3 25 s 3h 3 70 s 3h 4 29 s 2h b5 n methoxy 2 methoxymethoxy n methyl acetamide to a solution of weinreb amide 12 59 6 g 500 mmol in dichloromethane 500 ml was added while stirring n ethyldiisopropylamine 96 9 g 750 mmol and the colorless solution was cooled to 0 u00b0 c chloromethyl methyl ether 50 3 g 625 mmol was added at 0 u00b0 c over 15 min and the reaction mixture was stirred at 0 u00b0 c for 1 h and at rt for three days the pale yellow reaction mixture was washed with 1m hcl 500 ml and 5 brine 500 ml and the aqueous layers were extracted with dichloromethane 250 ml the combined organic layers were dried na 2 so 4 and evaporated to dryness affording 78.