N#N.[C:3]1(=[O:8])[CH2:7][CH2:6][CH:5]=[CH:4]1.[CH2:9]([N:16]([CH2:22]OC)[CH2:17][Si](C)(C)C)[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1.O>C(Cl)Cl.COC(C)(C)C.FC(F)(F)C(O)=O>[CH2:9]([N:16]1[CH2:22][CH:4]2[C:3](=[O:8])[CH2:7][CH2:6][CH:5]2[CH2:17]1)[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1A 3-neck, 1-L round bottom flask equipped with an addition funnel, internal thermometer, and N2 inlet at RT was charged with cyclopentenone (16.48 g, 0.20 mol) in 0.5 L of CH2Cl2. Benzyl(methoxymethyl)trimethylsilylmethylamine (5.0 grams, 21 mmol) and trifluoroacetic acid (TFA) (1.07 mL, 13.9 mmol) were added. To this mixture was added additional benzyl(methoxymethyl)-trimethylsilylmethylamine (40 g, 0.168 mol) dropwise via addition funnel over 1 hour with the reaction temperature being maintained below 25° C. (water bath). After the addition was complete, the mixture was stirred for 4 h. The mixture was washed with 1×100 mL 10% Na2CO3. The layers were separated and the organic layer was washed with 1×100 mL 23% NaCl. The organic extract was concentrated under reduced-pressure to give an oil. The oil was redissolved in methyl-t-butyl ether (250 mL) and extracted into 1M H3PO4 (200 mL). The aqueous layer was basified with 50% NaOH to pH 12. The product was extracted with methyl-t-butyl ether (250 mL). The layers were separated and the organic layer was washed with 23% NaCl. The layers were separated. The organic layer was charged with acetonitrile (50 mL) and silica gel (10 gms). The mixture was stirred 5 minutes and filtered through a silica gel pad (10 grams). The filtrate was concentrated to give the title compound (35.0 grams, 81.4% of theory), which was carried on to the next step without further purification. MS (ESI/APCl) m/z 216 (M+H)+.
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