153864-82-5Relevant articles and documents
Synthesis of α,β-Unsaturated Ketones Using Allylidenetriphenylphosphorane as a Three-carbon Unit
Hatanaka, Minoru,Imashiro, Ritsuo,Ueda, Ikuo
, p. 2253 - 2256 (1992)
3-Alkoxycarbonyl-2-ethoxy-2-propenylidenetriphenylphosphorane reacts in turn with alkyl halides and aldehydes in the presence of base via a one-pot procedure to give moderate to good yields of conjugated enol ethers.Hydrolysis of the conjugated enol ethers and subsequent decarboxylation provide a novel route to α,β-unsaturated ketones.
Allylidenetriphenylphosphorane as a Bifunctional Reagent: Synthesis of Cyclopentenones and α,β-Unsaturated Ketones with (3-(Alkoxycarbonyl)-2-ethoxy-2-propylidene)triphenylphosphorane
Hatanaka, Minoru,Himeda, Yuichiro,Imashiro, Ritsuo,Tanaka, Yasuhiro,Ueda, Ikuo
, p. 111 - 119 (2007/10/02)
When (3-(ethoxycarbonyl)-2-ethoxy-2-propenylidene)triphenylphosphorane (6) was allowed to react with α-bromo ketones 8a-d in dichloromethane in the presence of Cs2CO3 at room temperature, a annulation occured and led to the formation of the corresponding 2-ethoxycyclopentadienes 9a-d in excellent yields.Similarly, bromo thioester 8g underwent the annulation to give 4-(ethylthio)cyclopentadiene 9g.Secondary bromides 2-bromo-3-pentanone and 2-bromocyclohexanone also afforded tetrasubstituted cyclopentadienes 9e and 9f in moderate yields when 2 equiv of 6 was used.The annulation is belived to proceed through a sequence involving a stepwise alkylation at the γ position of 6 and an intramolecular Wittig reaction because of the fact that intermediate 11 was isolated.The resulting 2-ethoxycyclopentadienes 9a-g were converted quantitatively into the corresponding cyclopentenones 10a-g upon mild acid treatment.Furthermore, allylidenetriphenylphosphorane underwent a carbon elongation at both ends of the three-carbon unit via an alkylation-Wittig reaction sequence. (3-(tert-Butoxycarbonyl)-2-ethoxy-2-propenylidene)triphenylphosphorane (7) reacted first with alkyl halides and then with aldehydes in the presence of Cs2CO3 to give enol ethers 23a-f, which were converted into α,β-unsaturated ketones 20, 21, and 25c-f by hydrolysis of the enol ether and then decarboxylation.In this way, shogaol (29), the pungent principle component of ginger, was conveniently synthesized starting from 2-methoxy-4-methylphenol.
