A stereoselective one‐pot synthesis of spiropyrazolones through an organocatalytic asymmetric Michaeladdition and a formal Conia‐ene reaction has been developed. Depending on the nitroalkene, the 5‐exo‐dig‐cyclization could be achieved by silver‐catalyzed alkyne activation or by oxidation of the intermediate enolate. The mechanistic pathways have been investigated using computational chemistry and
Copper(II)-Catalyzed Asymmetric Henry Reaction of <i>o</i>-Alkynylbenzaldehydes Followed by Gold(I)-Mediated Cycloisomerization: An Enantioselective Route to Chiral 1<i>H</i>-Isochromenes and 1,3-Dihydroisobenzofurans
作者:Dengfu Lu、Yirong Zhou、Yajun Li、Shaobai Yan、Yuefa Gong
DOI:10.1021/jo201596p
日期:2011.11.4
By combining the copper(II)-catalyzed asymmetric Henryreaction of o-alkynylbenzaldehydes with subsequent gold(I)-catalyzed cycloisomerization, optically active 1H-isochromenes and 1,3-dihydroisobenzofurans were successfully synthesized in good overall yields with good to excellent enantioselectivities (up to 98%). Various substrates were investigated, and a correlation between the regioselectivity
Synthesis of Triazolo Isoquinolines and Isochromenes from 2-Alkynylbenzaldehyde via Domino Reactions under Transition-Metal-Free Conditions
作者:Rajesh K. Arigela、Srinivas Samala、Rohit Mahar、Sanjeev K. Shukla、Bijoy Kundu
DOI:10.1021/jo401929q
日期:2013.10.18
We describe two simple straightforward syntheses of triazolo isoquinolines (3) and isochromenes (7) from 2-alkynylbenzaldehydes (1) as a common synthon. The synthetic strategy for 3 involves formation of the (E)-1-(2-nitrovinyl)-2-(alkynyl)benzene species 2 via condensation of synthon 1 with nitromethane followed by a [3 + 2] cycloaddition/extrusion of the nitro group/regioselective 6-endo cyclization domino sequence. In yet another strategy, the synthon 1 was condensed with nitromethane followed by electrophilic iodo cyclization of the resulting 2-nitro-1-(2-(alkynyl)phenyl)ethanol (6) to furnish iodo isochromene derivatives. The salient feature of the above two strategies involves formation of the corresponding heterocycles under metal-free conditions in good yields.