By employing triethylamine as a catalyst, [3 + 2] coupling‐eliminationcascade of α,α‐dicyanoolefins with quinonemonoimines was realized. The reactions afforded various novelpterocarpenanalogues with generally moderate yields (up to 75%). In addition, a plausible reaction mechanism was proposed.
Organocatalytic asymmetric allylic carbon–carbon bond formation
作者:Thomas B. Poulsen、Mark Bell、Karl Anker Jørgensen
DOI:10.1039/b514564c
日期:——
bond-forming addition of activated alkylidenes to alkyl and aryl nitroalkenes has been achieved with high diastereo- and enantioselectivity. Chiral tertiary amine catalysts are used to give allyl intermediates which exhibit gamma-selectivity in the C-C bond forming step. The reactions proceed with up to >99:1 syn:anti ratio for both the alkyl- and aryl nitroalkenes with up 96% and 98% ee, respectively
organocatalytic addition of dicyanoalkylidenes to quinones catalyzed by Cinchona alkaloids leading to formation of 1,4-diketone derivatives with high diastereomeric ratios (up to >98 : <2 dr) and enantioselectivities (up to 99% ee) has been developed; the opticallyactive compounds obtained are useful for a number of transformations, e.g. the synthesis of opticallyactive alpha-aryl ketones.
Base-mediated [4+2] annulation of electron-deficient nitrobenzoheterocycles and α,α-dicyanoalkenes in water: Facile access to structurally diverse functionalized dibenzoheterocyclic compounds
A base-mediated [4 + 2] annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, 3-nitrobenzothiophenes, and 3-nitroindoles with α,α-dicyanoalkenes for the synthesis of structurally diverse dibenzoheterocyclic compounds was developed. The reaction proceeded smoothly via a tandem vinylogous Michaeladdition/cyclization/tautomerization/elimination process in water with cesium carbonate as base, affording