nmr cdcl 3 u03b4 194 1 169 2 138 4 135 4 130 1 129 7 129 3 128 4 128 1 127 2 65 0 62 7 46 9 30 9 cyclized intermediate 3 11 00 g 33 44 mmol and sulfuric acid 4 6 g were sequentially dissolved in 300 ml of methanol in a pressure bottle the bottle was sealed and the mixture was heated at 95 u00b0 c for 16 h the volatiles were evaporated the residue was neutralized with a saturated sodium carbonate solution and extracted three times with chloroform the combined organic extracts were washed with brine the organic solution was dried with sodium sulfate filtered and volatiles were evaporated the residue was converted to the oxalate salt in isopropanol to provide 13 60 g of compound 8 in a 95 yield mp 160 162 u00b0 c 1 h nmr cd 3 od u03b4 7 50 7 44 m 5h 7 11 7 07 m 2h 6 70 t 1h j 7 33 hz 6 59 d 2h j 7 79 hz 4 32 s 2h 3 62 s 3h 3 38 3 29 m 4h 2 47 2 27 m 4h 13 c nmr cd 3 od u03b4 174 8 165 4 145 3 131 1 129 9 129 1 129 0 128 7 118 5 115 0 60 0 56 4 51 7 29 8 this chemistry can be applied to 1 phenylethyl 4 piperidinone for a more direct route to carfentanil via anilino methyl ester 8 as shown below 1 phenylethyl 4 piperidinone 13 92 g 68 6 mmol aniline 8 94 g 96 mmol and potassium cyanide 6 25 g 96 mmol were added to 130 ml of isopropanol and cooled in.