I want to reduce double bond of flavone which has substituent at 6 position also. I tried with Pd/C and hydrogen but it is not working. Can any body help me which particular reducing agents I should use which can reduce double bond of lactone ring?
The C=C bond in the "lactone" of flavone is not a normal C=C bond (it's in an extended π system), so reducing it will be harder. Some people have done it using NaBH4 and a transition metal like nickel or cobalt, producing the desired compound in
I agree with Aaron, the C=C is part of conjugated system with C=O and can be reduced using NaBH4
* n mmol of substrate in methanol and 5n mmol of NiCl26H2O placed in a round bottomed flask attached to a reflux condenser and mounted over a magnetic stirrer. The contents of the flask were stirred magnetically and NaBH4 (5n mmol) was added to the flask. Thereafter, lots of NiCl26H2O (5n mmol) and NaBH4 (5n mmol) were added at intervals of 2 h until the starting material completely disappeared as observed by TLC.
See
--- Khurana, Jitender Mohan and Sharma, Purnima, Bulletin of the Chemical Society of Japan, 77(3), 549-552; 2004
If you are looking for stereoselective reduction, see
--- Zhao, Dongbing et al., Ruthenium-NHC-Catalyzed Asymmetric Hydrogenation of Flavones and Chromones: General Access to Enantiomerically Enriched Flavanones, Flavanols, Chromanones, and Chromanols Angewandte Chemie, International Edition, 52(32), 8454-8458; 201
I also do agree with above. You can also try to use strong hydride sources such as DIBAL. I just have found a several interesting papers describing the use of DIBAL for reduction of C=C bond in flavone moiety.
Journal of Medicinal Chemistry, 2016 , vol. 59, # 22 p. 10228 - 10243
Synthesis, 1981 , # 7 p. 574 - 576
Russian Chemical Bulletin, 2009 , vol. 58, # 12 p. 2465 - 2473
I suppose that the reaction should be conducted at low temperature (~-60 - -70 C) to ensure good chemoselectivity (side reduction of the ketone moiety).
I tried using the method suggested by you but it didn't work always we got starting back.. if any new method please suggest me.
With regards
Pratibha
n mmol of substrate in methanol and 5n mmol of NiCl26H2O placed in a round bottomed flask attached to a reflux condenser and mounted over a magnetic stirrer. The contents of the flask were stirred magnetically and NaBH4 (5n mmol) was added to the flask. Thereafter, lots of NiCl26H2O (5n mmol) and NaBH4 (5n mmol) were added at intervals of 2 h until the starting material completely disappeared as observed by TLC.
See
--- Khurana, Jitender Mohan and Sharma, Purnima, Bulletin of the Chemical Society of Japan, 77(3), 549-552; 2004
Strong reducing agent for double bond of lactone ring of flavone moiety?. Available from: https://www.researchgate.net/post/strong_reducing_agent_for_double_bond_of_lactone_ring_of_flavone_moiety [accessed Apr 24, 2017].