Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction.

A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes with no electron-withdrawing substituents. In this way, the aldehyde group serves as a traceless control ...

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پس از بررسی هر کدام از فاکتورهای نوع صنعت, نوع ضمانت نامه, نرخ بهره , نرخ تورم, ریسک اعتباری کشورها, کارمزد, ریکاوری, gdp, پوشش و وثیقه بر ریسک اعتباری صندوق ضمانت صادرات ایران مشخص گردید که همه فاکتورها به استثنای ریسک اعتباری کشورها و کارمزد بقیه فاکتورها رابطه معناداری با ریسک اعتباری دارند در ضمن نرخ بهره , نرخ تورم, ریکاوری, و نوع صنعت و ریسک کشورها اثر عکس روی ریسک اعتباری داردو پوشش, وثی...

Chiral N-heterocyclic carbene-catalyzed generation of ester enolate equivalents from α,β-unsaturated aldehydes for enantioselective Diels–Alder reactions

The catalytic generation of chiral ester enolate equivalents from α,β-unsaturated aldehydes with chiral N-hetereocyclic carbene catalysts makes possible highly enantioselective hetero-Diels– Alder reactions. The reactions proceed under simple, mild conditions with both aliphatic and aromatic substituted enals as substrates. Previous attempts to employ these starting materials as enolate precurs...

The influence of ligand side chain on the enantioselectivity of Lewis acid catalyzed Diels-Alder reactions.

The enantioselective Lewis acid-catalyzed Diels-Alder reaction of 3-(2-propenoyl)-1,3-oxazolidin-2-one 8 with cyclopentadiene was examined using a series of chiral mox ligands 2-6, deferring in the side chain at 2-position of the chiral oxazoline and in the nature of the substituent at the chiral center (4-position) of the oxazoline ring, and a combination of N-[(1R)-2-chloro-1-phenylethyl]-2-[...

Catalytic, Enantioselective Hetero-diels-alder Reactions of Aldehydes