Ring Size and Substituent Effects in Oxyanion-Promoted Cyclizations of Enyne-allenes: Observation of a Myers−Saito Cycloaromatization at Cryogenic Temperature
摘要:
A series of acetoxy-substituted enyne-allenes, fused to cyclopentene and cyclohexene ring systems, were synthesized and treated with methyllithium to generate the corresponding enolates. It was found that whereas the cyclohexannulated examples underwent either C-2-C-7 (Myers-Saito) cycloaromatization or C-2-C-6 (Schmittel) cyclization depending on their terminal subsituents, the cyclopentannulated examples either failed to cyclize altogether or underwent C-2-C-7 cyclization. Both of these results lie in contrast to the behavior of their benzannulated analogues, which underwent exclusive C-2-C-6 cyclization independent of substituents. These findings are rationalized on the basis of both ring strain effects and the steric encumbrance of the terminal alkynyl and allenyl subsituents.
Microwave-Assisted Copper-Powder-Catalyzed Coupling and Cyclization of β-Bromo-α,β-unsaturated Carboxylic Acids with 1,3-Diketones Leading to 2H-Pyran-2-ones
作者:Chan Cho、Son Ho、Ho-Sang Sohn
DOI:10.1055/s-0034-1379103
日期:——
Abstract β-Bromo-α,β-unsaturatedcarboxylicacids were coupled and cyclized with 1,3-diketones by microwave irradiation in the presence of a catalytic amount of copper powder and base to give the corresponding 2H-pyran-2-ones in good to high yields. β-Bromo-α,β-unsaturatedcarboxylicacids were coupled and cyclized with 1,3-diketones by microwave irradiation in the presence of a catalytic amount of
A recyclable metal-organic framework MOF-199 catalyst in coupling and cyclization of β-bromo-α,β-unsaturated carboxylic acids with terminal alkynes leading to alkylidenefuranones
作者:Son Long Ho、Il Chul Yoon、Chan Sik Cho、Heung-Jin Choi
DOI:10.1016/j.jorganchem.2015.05.040
日期:2015.8
β-Bromo-α,β-unsaturated carboxylic acids react with terminalalkynes in DMF in the presence of a catalytic amount of metal-organic framework MOF-199 along with a base under microwave irradiation to afford the corresponding alkylidenefuranones in good yields. The catalytic system could be easily recovered and reused 5 times without any loss of catalytic activity.
Pd/C-Catalyzed coupling and cyclization of β-bromo-α,β-unsaturated carboxylic acids with terminal alkynes leading to alkylidenefuranones
作者:Chan Sik Cho、Hyo Bo Kim
DOI:10.1016/j.jorganchem.2011.06.044
日期:2011.10
Palladium-catalyzed coupling of β-bromo-α,β-unsaturated carboxylic acids with terminalalkynes and subsequent regioselective 5-exo-dig cyclization produces (Z)-alkylidenefuranones in good yields.
CuI/amino acid-catalyzed coupling and cyclization of β-bromo-α,β-unsaturated amides with terminal alkynes leading to (3<i>Z</i>)-3-alkylidenepyrrol-1-ones