The reduction of −CH(OH) CCl3 group attached to a benzo-α-pyrone nucleus
The reduction of −CH(OH)CCl3 group attached to a benzo-α-pyrone nucleus has been studied for the first time, the reducing agents used being zinc dust and glacial acetic acid either in conjunction with conc. HCl or without it. It is found that the course of the reduction is highly affected by the constitutional factors. The following generalisation is made in this connection:
(a) on reduction with zinc and acetic acid, the group −CH(OH)CCl3 in the pyrone ring is reduced to −CH=CHCl group in case of hydroxy-coumarins; (b) the same group −CH(OH)CCl3 is reduced to −CH2CHCl2 group if (i) the reduction is carried out in conjunction with conc. HCl; (ii) the phenolic group −OH is either absent or is protected by acetylation.
KeywordsCoumarin Glacial Acetic Acid Reduction Product Acetyl Derivative Mixed Melting Point
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