Browsing by Author "Kippo, Takashi"

Now showing 1 - 2 of 2

Bromine-Radical-Mediated Synthesis of -Functionalized ,- and ,epsilon-Unsaturated Ketones via C-H Functionalization of Aldehydes
(2017-09-01)
Kippo, Takashi
;
Kimura, Yuki
;
Ueda, Mitsuhiro
;
Fukuyama, Takahide
;
Ryu, Ilhyong
The bromine-radical-mediated allylation reaction of aldehydes was studied. In the presence of V-65 as radical initiator, the reaction of aldehydes with allyl bromides gave beta,gamma-unsaturated ketones in good yields (13 examples, 45-84%). The reaction is triggered by hydrogen abstraction from the aldehyde by bromine radical to form an acyl radical, which undergoes an S(H)2'-type addition-elimination reaction with allyl bromides to give coupling products with liberation of bromine radical. Three-component coupling reactions comprising aldehydes, electron-deficient alkenes, and methallyl bromide also proceeded to give delta,epsilon-unsaturated ketones.
Bromoallylation of Alkenes Leading to 4-Alkenyl Bromides Based on Trapping of beta-Bromoalkyl Radicals
(2017-10-06)
Kippo, Takashi
;
Hamaoka, Kanako
;
Ueda, Mitsuhiro
;
Fukuyama, Takahide
;
Ryu, Ilhyong
A radical-chain addition of allyl bromides to aryl alkenes, vinyl ester, and vinyl phthalimide was studied in which elusive beta-bromodkyl radicals were trapped efficiently to give 5-bromo-1-pentenes in good to high yields (16 examples). A subsequent carbonylative radical cyclization with AIBN/Bu3SnH/CO was successful in giving the corresponding 3,5-disubstituted cyclohexanone derivatives in moderate yields. Synthesis of a piperidine ring was also successful by subsequent reaction with primary amine.