This document discusses various types of reduction reactions including: 1) Catalytic hydrogenation using metals like Pt, Pd, Ni, Ru, Rh to reduce double and triple bonds. 2) Hydride transfer reactions using sources like LiAlH4, NaBH4 to reduce carbonyl groups, nitro groups, and more. 3) Dissolving metal reductions using reactive metals like Li, Na in ammonia solution (Birch reduction) to reduce aromatics. 4) Specific reducing agents and conditions are described for reducing different functional groups selectively like carbonyls, nitriles, alkynes and more.

1. Reduction Reactions

2. Classification of reduction
reactions
 Catalytic hyrdogenation (H2 with metals)
 Hydride transfer reactions, using
hydride sources such as LiAlH4,
NaBH4,..
 Dissolving metal reductions (Na, Li in
ammonia solution) (Birch reduction)

3. Classification of reduction
reactions
 Replacement of oxygen by hydrogen
 Removing oxygen from the substrate
 Reduction with cleavage
 Reductive coupling

4. Catalytic Hydrogenation
 Addition of H2 to unsat. bond (double ,
triple bonds, NO2 , CN,..
 Without catalysts ,it needs 480 co
 Pt group metals (Pd, Ni ,Ru and Rh)
used as catalysts
 Can be selective reduction, depends
on conditions

5. Catalytic Hydrogenation

6. Catalytic Hydrogenation

7. Pd/C reduction
 Pd powder spread on charcoal after
reduction of PdCl2 with H2
 Homogenous catalyst, can be recovered by
filtration

8. Raney Nickel
 Treatment of Al-Ni alloy with NaOH
 To reduce alkenes, alkynes, nitriles aromatics
and carbonyl compounds
 Syn addition product

9. Raney Nickel
 Hydrogenolysis: removal of sulphur (C-S
to C-H) in desulphurization reaction
 Use after open immediately????

10. PtO2( Adams catalyst)
 PtO2 reduced to Pt with H2

11. Lindlar`s catalyst
 Pd supported with CaCO3 instead of
charcoal,then treated with Pb to deactivate.
 Selective reduction of alkynes to Z-alkenes
only via syn addition

12. NaBH4
 Selective (chemoselectivity) reagent
 White crystals, safe and easy to handle
 Reduces aldehydes, ketones.
 Can`t reduce esters ,acids, amides

13. NaBH4
Generally
Still reducing agent

14. NaBH4
Luche reduction

15. LiAlH4
 Powerful reducing agent compared to
NaBH4 due to weaker Al-H bond.
 Pure sample is white but commercially
is grey????
 Dangerous, reacts violently with water
 Reduce aldehyde, ketones, esters,
amides and nitro compounds.

16. LiAlH4

17. DIBAL
 Selective reagent (alkyne to alkene, ester
or ketone to aldehyde).
 Specialist reductant of nitrile to aldehyde

18. Borane
 BH3 gas dissolved in THF or Et2O or DMS
 Selective reducing agent
 Hydroboration is syn addition, highly
regioselective

19. Borane Regioselectivity

20. Borane chemoselectivity

21. Borane
Amide to amine
Dialkyl borane

22. CBS ???
 Borane complexed with oxazoborolidine
 Enantioselective reduction of ketones
 So, CBS is a catalyst, not reagent

23. CBS ???
 R,R` difference is very important
 High ee, high yield
 Easy recovered

24. Wolff-Kishner reduction
 Reduction of aldehydes, ketones to alkane
 Using hydrazine in basic media

25. Metal dissolving reduction
 Dissolving Li or Na in NH3 solution
 Birch reduction in case of aromatics
 Good access to cyclohexadienes

26. Metal dissolving reduction
+I, -I effect

27. Metal dissolving reduction
Why 1,4 not 1,3 ???

28. Clemmensen reduction
 Kind of electron reduction reactions
 Zinc metal in Conc. HCl
 Carbonyl to alkane (CH )
2
Carbenoid mechanism

29. Asymmetric hydrogenation
 Using catalytic amounts of chiral ligands
with H2.

30. Asymmetric hydrogenation

31. Staudinger reduction
 Azide to amide (possible via hydrogenation)
 Mild conditions