Tandem cross-Rauhut–Currier/cyclization reactions of activated alkenes to give densely functionalized 3,4-dihydropyrans
摘要:
A novel tandem cross-Rauhut-Currier/cyclization reaction between alpha,beta-unsaturated ketones was developed. Using DABCO (20 mol %) as the catalyst, a series of densely functionalized 3,4-dihydropyrans were obtained in excellent yields and stereoselectivities (up to 98% yield, >99:1 dr). A tentative catalytic cycle was proposed with key intermediates confirmed by ESIMS studies. (C) 2011 Elsevier Ltd. All rights reserved.
Organocatalytic Asymmetric [4+2] Cycloaddition of 1-Acetylcyclopentene and 1-Acetylcyclohexene for the Synthesis of Fused Carbocycles
作者:Utpal Nath、Subhas Chandra Pan
DOI:10.1002/ejoc.201701238
日期:2017.11.24
The first organocatalytic asymmetric [4+2] cycloaddition reaction employing 1-acetylcyclopentene and 1-acetylcyclohexene is described. Enones having cyano group are used as the dienophile partner in this method. The reaction provides a useful practical route for the synthesis of bicyclic fused carbocycles having four contiguous stereocentres.
Novel transformation of methylenecyclopropanes (MCPs) with acyl cyanoalkenes has been achieved to give oxaspiro[2.5]octenes. This annulation is successfully catalyzed by magnesium halides under mild reaction conditions, and shows a broad functional group tolerance. The reaction includes a rare reaction course, which involves an intramolecular oxa-Michael addition of Mg enolate after the ring opening
Synthesis Route to Pyrrolones from α-Cyano α,β-Unsaturated Ketones and α-Isocyano Esters by Oxidative Dearomatization of 2-Aminofuran Intermediates
作者:Anil K. Mahida、Someshwar B. Kale、Utpal Das
DOI:10.1002/ejoc.201701194
日期:2017.11.24
A straightforward catalyst-free, ligand-free, and metal-free synthesis of 2-aminofurans through [4+1] cycloaddition of isocyanoacetates and electron-deficient alkenes is developed. The products are obtained in high yields without any column chromatography. Oxidative dearomatization of the furan products leads to pyrrolones in high yields.
Diastereoselective synthesis of highly substituted tetrahydroquinolines using benzoylacetonitrile via aza Diels–Alder reaction
作者:Arunan Palanimuthu、Chinpiao Chen、Gene-Hsian Lee
DOI:10.1016/j.tetlet.2021.153063
日期:2021.5
Diastereoselective aza-Diels–Alder reaction between in situ generated 2-aminophenyl-substituted enones and α-cyano-α,β-unsaturated aromatic ketone has been developed. In the presence of TEA as a catalyst prepared highly substituted tetrahydroquinolines with an all-carbon quaternary center in an in situ fashion. Both tetrahydroquinoline isomers (exo and endo) with excellent diastereoselectivity and
Dienamine-Mediated Asymmetric Inverse-Electron-Demand Hetero-Diels-Alder Reaction of Linear Deconjugated Enones: Diversity-Oriented Synthesis of 3,4-Dihydropyrans
作者:Rajendra Maity、Subhas Chandra Pan
DOI:10.1002/ejoc.201601575
日期:2017.1.26
The dienamine‐mediated inverse‐electron‐demandhetero‐Diels–Alderreaction of deconjugated enones having α‐CH groups and electron‐deficient oxadienes with a cyano group allows the efficient and enantioselectivesynthesis of 2,4‐stereogenic 3,4‐dihydropyrans. With a primary amine and benzoic acid, high yields and excellent enantioselectivities are obtained for a range of 3,4‐dihydropyrans.