| 摘要 |
A process for the preparation of a compound of general formula II: <IMAGE> II wherein R1 is hydrogen, or C1-C10 hydrocarbyl or heterocyclyl having 3 to 8 ring atoms, either of which may optionally be substituted; each R2, R3, R4 and R5 is independently hydrogen or C1-C4 alkyl; A is an optionally substituted aromatic or heteroaromatic ring system; and R21 is hydrogen, halogen, OH or OCONHR1, wherein R1 is as defined above; the process comprising cyclizing a compound of general formula III: <IMAGE> III wherein A, R2, R3, R4, R5 and R21 are as defined in general formula II and R25 is a leaving group such as a halogen atom; under basic conditions.
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