Name Reactions

MEERWEIN PONNDORF VERLEY REDUCTION
OPPENAUER OXIDATION
BECKMANN REARRANGEMENT
MICHAEL REACTION

1. ADVANCE IN ORGANIC CHEMISTRY PRESENTED BY SURENDRA KUMAR GAUTAM DEPT. OF PHARMACY GLA UNIVERSITY

2. CONTENTS MEERWEIN PONNDORF VERLEY REDUCTION OPPENAUER OXIDATION BECKMANN REARRANGEMENT MICHAEL REACTION NAME REACTIONS

3. 1. MEERWEIN-PONNDORF VERLEY REDUCTION The reduction of carbonyl compound to alcohols using aluminium iso propoxide is known as MPV reduction . MECHANISM Al t- butoxide is not used in reduction because of absence of H . The first step involved the transfer of hydride from the aluminium iso propoxide to the carbonyl compound through a 6 membered cyclic transition state to produce a mixed alkoxide and acetone . The acetone has to be quickly distilled off to take the reaction in the forward direction.

4. In second step isopropanol is used which exchanges a proton with the mixed alkoxide to liberate desired alcohol.

5. Specificity of Aluminium iso propoxide It is soluble in both alcohol and hydrocarbon . It’s boiling point 140ºC-160ºC. which allows acetone to be distilled off to shift the equilibrium the forward direction. The most important property in the side reaction is that aluminium alkoxide are much less polar than alkali metal alkoxide . Since , Al-O bond is more covalent, it undergoes little dissociation to produce basic kind of polymerization reduction. So this side reaction is negligible in this reaction condition . APPLICATIONS To produce conversion and α, β- unsaturated carbonyl compound to α, β- unsaturated alcohol .

6. Reduction of α- halogenations ketone , keto esters etc . Examples

7. 2. OPPENAUER OXIDATION It is the reverse of MPV reduction . It involves the oxidation of 2º alcohol to ketones with the help of aluminium alkoxide in the presence of a hydride acceptor like acetone. Normally used alkoxide are aluminum tri iso propoxide or Al-tri- tert - butoxide . 1º alcohols may also be oxidized to aldehydes if acetone is replaced by a better hydrogen acceptor like as p- benzoquinone or aromatic ketone .

8. MECHANISM Aluminum alkoxide produce the alkoxide of the particular 2ºalcohol which is to be oxidized. The alkoxide of the 2º alcohol alcohol undergoes a internal hydride transfer with acetone forming the desired ketone through a cyclic transition state .

9. APPLICATIONS Particularly useful for oxidizing unsaturated 2º alcohol because double bonds are not affected . Examples

10. 3. BECKMANN REARRANGEMENT The rearrangement of oxime under the influence of a variety of acidic reagent to N- substituted amide . PCl 5 is commonly used as a catalyst in Beckmann rearrangement; but conc. H 2 SO 4 , formic acid and silica etc. have been used successfully. e.g . benzophenone oxime is converted into benzanilide in the presence of PCl 5 . The role of these catalysts is to convert the hydroxyl group into a better leaving group .

11. MECHANISM

12. It has been found that the EWG (-R) attached to the migrating aryl group retard the rate of reaction. The presence of EWG (+R) on the otherhand , has an accelerating influence .

13. Examples DRWABACKS Anti- syn isomerism of oxime Beckmann fragmentation

14. Anti- syn isomerism of oxime Some reaction condition can lead to syn anti- isomerization of the oxime occurring at the rate transfer than the Beckmann rearrangement then a mixture of product will be obtained . Rate (Step-1˃Step-2) – product mixture Rate (Step-2˃Step-1) –pure product . Fragmentation Occurs if one of the oxime substitutents can give rise to a very stable carbocation and subsequent formation of nitrile .

15. APPLICATIONS Configuration of keto oxime can be obtained. Aldoxime under B.R condition may dehydrate to nitriles .

16. 4. MICHEAL REACTION The 1, 4 addition of an enolate anion to an α, β-unsaturated carbonyl compound to yield a 1, 5-dicarbonyl compound is a method for the formation of carbon-carbon bonds and is called as Michael reaction or Michael addition. The 1, 4-addition to α, β-unsaturated carbonyl substrate is also called a conjugate addition. Various other 1, 4-addition is known and sometimes referred to as Michael like additions .

17. MECHANISM Step-1:- first an acid-base reaction. Hydroxide functions as a base and removes the acidic α-hydrogen giving the reactive enolate . Step-2:- The nucleophilic enolate attacks the conjugated ketone at the electrophilic alkene C in a nucleophilic addition type process with the electrons being pushed through to the electronegative O giving an intermediate enolate . Step-3:- an acid-base reaction. The enolate deprotonates a water molecule recreating hydroxide and the more favourable carbonyl group.

18. Examples

19. THNAK YOU!!!