Question

5. Give the reactions for the following synthesis using benzene and any inorganic reagent. OEt steps HO 6. Give the reactions for the following synthesis using and two carbon functional group and any inorganic reagent. (hint: use Wittig and Gilman reactions) steps ОН —

Answer 1

Benzene react with 4-ethoxy-4-oxobutanoic acid in acidic condition to form ethyl 4-oxo-4-phenylbutanoate. Further, sodium borohydride in THF reduces only ketone and not ester to produce hydroxyl ester derivative which is cyclized in presence of acid to form final product.

Succinic acid react with thionyl chloride to form succinyl dichloride which reacts with dimethyl lithium cuprate (Gilaman reagent) to form hexane-2,5-dione. Further, acidic bromination of diketone gives 3-bromohexane-2,5-dione as major product. Then, DBU base is used for dehydro halogenation to form (E)-hex-3-ene-2,5-dione. Alkene formed undergo Gilman reagent addition to form 3-ethylhexane-2,5-dione. Further, acidic bromination followed by dehydrohalogenation forms (E)-3-ethylhex-3-ene-2,5-dione. Then, Gilman reagent addition gives 3,4-diethylhexane-2,5-dione as major product. Finally, wittig reaction of the diketone followed by hydrogenation gives 4,5-diethyl-3,6-dimethyloctane

HO 4-ethoxy-4- oxobutanoic acid NaBH4, THF Ht, heat H + benzene o onomeno why-dynay boy OH SOCI, DCM CI (CH3)2Culi Brz, AcOH но succinc ad succinic acid succinyl dichloride hexane-2,5-dione Br 0 3-bromohexane- 2,5-dione DBU, THF O DBU, THF Brz. AcOH (CH3-CH2)2Culi (E)-3-ethylhex-3- ene-2,5-dione (E)-hex-3-ene-2,5- dione 3-bromo-4- ethylhexane-2,5- dione 3-ethylhexane-2,5- dione (CH3-CH2)2Culi PPh Hz. MeOH NaH, THF TY 3,4-diethylhexane- 2,5-dione (25,6E)-4,5-diethyl- 3,6-dimethylocta- 2,6-diene 4,5-diethyl-3,6- dimethyloctane