RETROSYNTHETIC APPROCH TO ORGANIC SYNTHESIS FUNCTIONAL GROUP INTERCONVERSION

RETROSYNTHETIC APPROCH TO ORGANIC SYNTHESIS FUNCTIONAL GROUP INTERCONVERSION Dr. Shaikh S. Nizami Department of Chemistry University of Karachi

FUNCTIONAL GROUPS INTERCONVERSIONS

CONTENTS ,[object Object],[object Object],[object Object],[object Object],[object Object]

Definition of F unctional G roup I nterconversion ,[object Object]

Definition of F unctional G roup I nterconversion ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Why FGI is needed? ,[object Object]

Why FGI is needed? ,[object Object],[object Object],[object Object]

Importance of FGIs ,[object Object],[object Object],[object Object]

Importance of FGIs TM First step in the retrosynthetic analysis of TM could be functional group interconversion to an alcohol But which alcohol ?

Importance of FGIs FGI i FGI ii TM

RETROSYNTESIS FGI + TM Matched Latent Polarity (Consonant) i

RETROSYNTESIS FGI ii Mismatched Latent Polarity (Dissonant)

Functional group containing heteroatoms ,[object Object]

a) Carboxylic acid and their derivatives ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transformations of carboxylic acid derivatives SOCl 2 or PCl 5 H 2 O NH 3 RO - H 2 O H 2 O H + / R’OH H 2 O

b) Aldehydes, ketones and their derivatives ,[object Object],[object Object]

b) Aldehydes, ketones and their derivatives ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Transformations of aldehydes aldehyde R’NH 2 R’=alkyl, aryl,(imine) R’=NMe2 (hydrazones) R’=OH (oxime) H 2 O HS(CH 2 ) 3 SH/H+ 2R’OH/H +

c) Alcohols and their derivatives ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Interconversions of alcohols and halides SOCl2 or PCl5 HO - HBr HO -

Use of a sulphonic ester as a leaving group R’SO 2 Cl Nu - + R’SO 3 -

Interconversions between the three oxidation levels a,b & c above ,[object Object]

Oxidation ,[object Object],[object Object]

Oxidation Primary alcohol PCC or PDC CrO 3 /H + Secondary alcohol PCC or PDC PCC= pyridinium chlorochromate PDC= pyridinium dichromate

Reduction Esters LiAlH 4 + R’OH Amides LiAlH 4 Nitriles LiAlH 4 1 eq. DIBAL-H Low temp.

Unsaturated Hydrocarbons H 2 ,Pd/C OsO 4 O 3 HBr RCO 3 H BH 3 ,NaOH/ H2O 2

Removal of Functional Group Alcohol to corresponding hydrocarbon Alcohol Dehydration Alkene Alkane Hydrogenation

Removal of Functional Group Clemmensen Wolf-Kishner Zn,HCl NH 2 NH 2 ,KOH Aldehydes/ ketones to hydrocarbons

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