Transition Metal-Free Cascade Cyclization of Epoxy-Ynamides: To Go for 1,3-Oxazines or 1,4-Oxazines?
摘要:
An approach to both 1,3- and 1,4-oxazines is developed by the cascade cyclization of epoxy ynamides under transition metal-free conditions. Thus, while 1,3-oxazines are obtained in a regio- and stereoselective manner by using base, cyclization of epoxy ynamides with sodium azide as a nucleophile results in 1,4-oxazines. Deuterium-labeling experiment demonstrates the role of water as a proton source in the formation of 1,4-oxazines. Epoxy tethered alkyne precursors provide 1,4-oxazines that undergo click reaction.
Ruthenium-catalyzed [2+2] cycloadditions of bicyclic alkenes and ynamides
作者:Karine Villeneuve、Nicole Riddell、William Tam
DOI:10.1016/j.tet.2005.11.081
日期:2006.4
Ruthenium-catalyzed [2+2] cycloadditionsbetweenbicyclicalkenes and ynamides were investigated. The ynamide moiety was found to be compatible with the ruthenium-catalyzedcycloaddition conditions giving the corresponding cyclobutene cycloadducts in moderate to good yields (up to 97%). Diastereoselective cycloaddition utilizing chiral cyclic ynamides were also examined and a low to moderate level
N-Alkynylated sulfoximines have been obtained by copper-catalyzed cross-coupling reactions starting from NH-sulfoximines and bromoacetylenes in moderate to good yields. The reaction conditions are mild, and the substrate scope is wide.
Visible-Light-Promoted Oxidative Amidation of Bromoalkynes with Anilines: An Approach to α-Ketoamides
作者:Ke Ni、Ling-Guo Meng、Kuai Wang、Lei Wang
DOI:10.1021/acs.orglett.8b00586
日期:2018.4.20
A convenient and practical synthetic route to α-ketoamides from bromoalkynes and anilines through phototriggered organic transformations via a C–N cross-coupling and an oxidation of C≡C was developed. The reaction could be furnished without an external photocatalyst at ambient conditions, and a wide range of α-ketoamides were obtained in good yields.
Stereoselective Synthesis of Trisubstituted Alkenes through Sequential Iron-Catalyzed Reductive<i>anti</i>-Carbozincation of Terminal Alkynes and Base-Metal-Catalyzed Negishi Cross-Coupling
作者:Chi Wai Cheung、Xile Hu
DOI:10.1002/chem.201504049
日期:2015.12.7
stereoselective synthesis of trisubstituted alkenes is challenging. Here, we show that an iron‐catalyzed anti‐selective carbozincation of terminal alkynes can be combined with a base‐metal‐catalyzed cross‐coupling to prepare trisubstituted alkenes in a one‐pot reaction and with high regio‐ and stereocontrol. Cu‐, Ni‐, and Co‐based catalytic systems are developed for the coupling of sp‐, sp2‐, and sp3‐hybridized
Palladium-Catalyzed Synthesis of Fluorescent Benzo[4,5]imidazo[1,2-a]pyridines through Annulation Reaction of Benzimidazoles and Alkynyl Bromides with Internal Alkynes
An efficient synthesis of fused azapolycycles based on (benz)imidazole and pyridine scaffolds has been developed. In all cases, the first nucleophilic addition of (benz)imidazoles to alkynyl bromides in tert-pentyl alcohol can proceed in a stereoselective manner to provide (Z)-N-(1-bromo-1-alken-2-yl)benzimidazoles at 110 °C. Sequentially, these adducts containing alkenyl bromide can undergo Pd-catalyzed