13C NMR (DMSO-d6, 100 MHz): δ = 35.2, 36.8, 61.5, 107.4, 122.5, 125.4, 127.8, 136.1, 143.8, 176.9;
1H NMR (DMSO-d6, 400 MHz): δ = 2.64 (t, J = 6.8 Hz, 2H), 3.44 (s, 2H), 3.59 (q, J = 6.8 Hz, 2H), 4.62 (t, J = 5.2 Hz, 1H), 6.64 (d, J = 7.6 Hz, 1H), 6.78 (d, J = 7.6 Hz, 1H), 7.08 (t, J = 7.2 Hz, 1H), 10.30 (s, 1H);
A new and efficient manufacturing technology is disclosed in the present work for the preparation of 4-(2-hydroxyethyl)-1,3-dihydro-2H-indol-2-one, which is a key intermediate for ropinirole hydrochloride. The whole process gives the target molecule in 71% overall yield with 99% purity. In the final step, a novel nitro reduction/ring-closing/debenzylation takes place in one pot. All the intermediates can be used directly for the next step without purification in this process.
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