Question

Using as few steps as possible, show how you cloud take cyclohexanone and prepare the compounds below. You may use any compounds or reagents that you wish.
Provide each step and reagents

Answer 1

1)

i)Presence of weak acetic acid make conditions slightly acid. Under slightly acidic conditions carbonyl O get protonated. H2O abstract proton from ? position and carbanion generated get stabilized in polarized C=O bond.

ii) Reversal electron density on ?- C cause nucleophilic attack at polarized Br-Br bond and 2-Bromocyclohexanone formation takes place. (AcOH has main role as Br-Br bond polarizer)

iii)Then a bulky non-nucleophilic base t-BuO^- cause ?- elimination reaction and forms Cyclohex-2-enone.

iv) Ph2CuLi (Gilman reagent) undergo exclusively conjugate addition across enone and if we supplied reaction with methyl iodide (Me-I) at the same time then second addition at ? position also takes in same reaction and formation of final product takes place.

Br )Ph2CuLi (Gilman Me H2O/AcOH reagent) r2 Il) Me-l Ph 2-Bromo- cyclohexanone Cyclohexanone Cyclohex-2-enone 2-Methyl-3-phenyl -cyclohexanone Mechanism Br H20 t-BuO LI TO H3CI Me Gilman reagent -Lil Ph Ph Ph Ph Cu 1,4-addition

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2)

i) SeO2 (selenium dioxide) is selective oxidizing agent which oxidizes ? position in carbonyl compounds to oxo (C=O group). Cylohexanone on treatment with SeO2 forms cyclohexane-1,2-dione.

ii)Cyclohexane-1,2-dione on treatment with 1 equivalent of phosphorus Ylide forms C=C bond on reaction one of the C=O group. This reaction is known as Wittig reaction.

iii)Anathor C=O group on reaction with Grignard reagent PhMgBr and on subsequent acid hydrolysis will give the required product.

Ph OH CH 2 CH2 Wittig reaction CH2-PPh3 PhMgBr/ether i)H3Oe SeO2 a-oxidationPRosphorus ylied2methylene2-methyene-1-phenyic yclohexanol 2-methylene -cyclohexanone 2-methylene-1-phenylc yclohexanol 1equivalent

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3)

i)Base Lithium diisopropyl amide (LDA) generates carbanion which on treatment with 3-Bromoethannitrile shows SN2 reaction and forms required product.

3-bromopropanenitrile CN CN LDA SN2 cyclohexanone 3-(2-oxocyclohexyl)propanenitrile

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