HClO4·SiO2-mediated improved isomerization of glycidic esters to α-hydroxy-β,γ -unsaturated esters: Application in the formal synthesis of (R)-Baclofen and β-phenyl GABA analogues
An efficient isomerization of glycidic esters to corresponding allylic alcohols, viz. α-hydroxy-β,γ -unsaturated esters has been brought about using HClO4·SiO2. Five of these allylic alcohols underwent selective SN2' nucleophilic substitution to generate γ-azido-α,β-unsaturated esters which were readily converted to an antispastic drug Baclofen and four other β-phenyl GABA analogues.
Basak, Ranjan,Dharuman, Suresh,Reddy, Y. Suman,Doddi, Venkata Ramana,Vankar, Yashwant D.
p. 325 - 327
(2012/06/01)
Co-catalyzed reductive cyclization of azido and cyano substituted α,β-unsaturated esters with NaBH4: enantioselective synthesis of (R)-baclofen and (R)-rolipram
Sodium borohydride in combination with a catalytic amount of CoCl2 has been found to be an excellent catalytic system in reductive cyclizations of suitably substituted azido and cyano groups of α,β-unsaturated esters to afford γ and δ-lactams in high yields. The process has been demonstrated for the enantioselective synthesis of (R)-baclofen, (R)-rolipram, and (R)-4-fluorophenylpiperidinone, a key intermediate for (-)-paroxetine.
Paraskar, Abhimanyu S.,Sudalai, Arumugam
p. 4907 - 4916
(2007/10/03)
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